So I think it's time I got around to setting up an install of Windows 7. Although I'm not sure when that will happen as I'll need to persuade my boss to foot at least some of the cost ($450 is a little more than I can really afford right now =/). But, when I do, it'll be a standalone version of Ultimate (this is necessary due to required language options). I won't be getting an upgrade version as I intend to keep my current installation of XP.
I also want to minimize the disruption to my work which brings me onto my main questions:
- Is it possible to install Windows 7 around an existing installation of XP on the same hard-drive (for which a new partition will need making for Windows 7) or will I need to uninstall it first then put XP back on after installing Windows 7?
- I'm planning on installing the 64 bit version, but if I then find it's not compatible with some programs (specifically the ones I require for work) is it possible to then install the 32 bit version instead? Or once you've installed one, is the other no longer usable?
- What are the compatibility options like?

APC mag has various combinations that will answer your first part, though I've yet to run XP and then 7 alongside. It's on my todo list for a test machine at work.

Well with microsoft OS' you have to install them in release order so dual booting 7 and xp will be easy as long as you can create the new partition for 7
I've never met an app yet that can't run in 32bit mode under Win7 and that includes some weird small scale freeware stuff from several years ago before 64bit was common (or even available). In fact I've never met an app that refused to run in 7 at all, the closest was interstate 76 I got from GOG but that was as much my shitty video card as the program
When you say compatibility options, I presume you mean the compatibility mode settings. They're the same as XP with the addtion of XP SP2 and SP3, server 2003 and server 2008. I don't THINK there's a vista option but since 7 is only the version of vista they had time to finish, it hardly needs it
My verdict as a qualified IT person: Go OOOOOON you know you wanna. What are ya, chicken? BUCK BUCK BUCK

I believe the disc contains either 32 or 64-bit version, not both (either that or my version is "speshul", which may very well be the case since I got both copies through some student deal to get them cheaper). If it contains both I would guess it installs the "appropriate" version for your machine (ie. it detects a 64-bit machine, it'll install 64-bit).
16-bit apps and installers won't run on the 64-bit version, but will in most cases run in a virtual machine (like the XP Mode you can install for free on 7 Pro and Ultimate)
XP Mode is, admittedly, pretty neat. It's MS VirtualPC with a preconfigured XP image. It's got a seamless mode (I forget what they actually call it, it's "Unity" in VMWare) so you won't have to see the XP desktop, and shortcuts to stuff you install in the VM are put in your real start menu so it's easy to start the apps from within Win7 (the VM will start up and launch the application without showing the XP desktop).
Vista, Vista SP1, and Vista SP2 are there (for me at least, on 7 Ultimate x64).

I posted this for something else but . . . rather than rewrite it . . . I'm doing a copy, paste. Hope the video is of some use to you . . . =)
I couldn't get the CPU I wanted with the Win 7 Pro so I bought the desired CPU with Win 7 64 Home and upgraded to Win 7 Pro 64 with the "anytime" method.
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The main obstacle for most folks wanting to try XP mode is it is only available to Professional and Ultimate Win 7 users. Although it involves an extra cost many might not know that they can upgrade to Win 7 Professional for $79 using the "Anytime Upgrade" feature in Win 7, you can also buy the Anytime Upgrade key from BestBuy (they try to sell you the $199 Pro upgrade, insist on the "Anytime Upgrade"), seems all versions of Win 7 are always installed and you only need the key to upgrade. Cost may vary depending on location.
I suggest anyone interested in trying the XP Mode should look at the videos at the bottom of this page for a walkthrough of the XP mode.
It is simple to set up the XP mode, download three files (the first is nearly 500 MB) and install them in the correct order, put the game on a USB stick. There is a small tool bar at the top of the XP screen which allows you to activate a USB device, do that after which you navigate to the install file using XP's Windows Explorer and install as usual. It is a fully working version of XP SP3 so you will need to update using Windows Update and add a firewall and AV if you are using it while there is an active internet connection.
Edit: BTW, XP Mode does not support 3D graphics.

The standalone version of Ultimate has both 32-bit and 64-bit DVDs using the same license key, and both can be installed at any time (although not at the same time, of course).
I have been using 64-bit Ultimate myself since October '09, and found it to be rock solid with any programs I possess. The only caveat is that some older programs, especially games, can benefit from being installed to a directory other than \Program Files or \Program Files (x86) due to how UAC works. This is particular to games that keep their saves folder in the install directory, or programs that locate their configuration files in the install directory.

I think the only versions of Windows that have specific 32/64bit versions are the OEMs, the retail packs seem to all have both

I went for a dual boot solution.
I bought a new hard disk and installed it, temporarily disconnecting the old XP drive.
I installed Windows 7, then re-connected my old XP drive, and set the boot order in my bios to boot the WIndows 7 drive first.
I then used the bios boot menu to boot into the XP drive when
I needed to use XP.
In WIndows 7 and XP I mounted the other OS's drives so I can easily access files from either OS.
Eventually over time I booted XP less and less, and only use it rarely now.
This method is good because you get to keep all your old data in it's pristine state, easily accessed, and you can also boot XP if you ever need to.

Yes. The Windows XP installation will be moved to a folder called Windows.old. You can move what you need out of it and then delete it later.
Absolutely. 64-bit includes a 32-bit subsystem, 32-bit just works. Don't worry about it, it'll go fine. But where there is a 64-bit alternative, you should use it to maximise on resource usage. Do not use 64-bit browsers, however, as most plugins will not work with them.
Beautiful and, for the most part, not needed. But they work very well when you do need them. Mostly I use them just to disable Aero before launching Source Engine games.
Basically, don't worry. In Windows 7, things are gonna work. Seriously. And if you find yourself needing it, XP Mode works quite nicely with non-game things (but is only available in Professional, Ultimate and Enterprise).
Every game I've tried from >2001 has worked. Pre 1997 Windows mode stuff is out of the question since it's all mostly 16-bit (64bit Windows removes WOW for 16-bit, which is a terrible shame). Thief works wonderfully, as I stated in a forum post at some point with a guide and everything. DOSBox and ScummVM work perfectly. There's even a 64-bit build of ScummVM which I have had no trouble with yet.
Go for it. Don't stick around on XP, you need to get movin' on up!

The only thing that I had problems with so far on Windows 7 x64, was Starcraft. But it can be easily fixed if you run the game as administrator and with Windows 98 / ME compatibility settings. Other than that, I haven't had any problems with whatever software I've used so far (that includes games, music production software, some development tools and other crap).

You say that like its a flaw rather than a feature. I use 32bit IE for most browsing but when I'm capped or just not in the mood to be driven to a state of near epilepsy by evony ads with flashing tits taking up 2/3 of the screen, I run 64bit IE and the net is not only better for my eyes but also loads quickly again. Remember those days when pages used to be measured in kilobytes rather than megabytes...

Thanks for the info all.
While I like the idea of putting Win7 on a separate drive, I simply don't have the cash and if I did have the cash for a new drive I still wouldn't have a slot on the motherboard to connect it to. I already have 3 hard drives in this PC as it is. And the one with XP on it has a good 100 gigs of space which is not being used. So it makes sense to shrink that partition and put Win7 around it.
Besides, I should probably get a new sound card when I have cash for hardware as I'm still using an old Soundblaster sommat or other.
And yeah, I could just format the drive and go right to Win7, but I'd rather have XP to fall back to due to work. For one thing, it'll take several days to reteach the main program I use as a translation aid and the makers of that didn't make exporting it's memory an option.
So now to hope I can persuade the boss to pay half the cost or so. Curse MicroSoft for ripping us off with their insane regional pricing.

I'd recommend you create two partitions and install 7 in one. That's actually easier to do with the XP setup. But only if you're intent on wiping the whole drive and installing both OS from scratch. To be honest, if you're getting Ultimate then you have no use for XP anymore though.
I fell straight into using 7. I had an XP partition for a while and never had a use for it. So it got deleted.

Is there a utility like EasyBCD but for xp? I would like to install different windows but keep the xp bootloader.

I'd probably avoid a third party firewall for now, and stick with Windows 7 Firewall (boo!). I had a lot of issues with hard crashes when trying to do things online. Whether it was multiple downloads, or just opening Firefox when another application was trying to sign in - the PC would lock up completely.
No error reporting, alt ctrl deleting, or mouse movement - just a complete crash needing a hard reset.
I found a surprisingly high number of people asking on various forums for an answer, unfortunately this was during the beta (I wasn't able to find anything recent, nor were there answers for people anyway). I did come across a post from a user who was suggesting there was something buggy about the DNS handling code within Windows 7.
I was extremely tired, overloaded with information, so that's about as much detail as I can give you. I was using the free version of ZoneAlarm, uninstalled it a week or so back and haven't had a lock up since.
If you do get Win7 Pro 64 bit and find a third party software firewall that doesn't bring the OS to it's knees, please let me know.
EDIT: Oh right, you want Ultimate. Should be roughly the same thing.. Roughly.