Hey guys, this may not be the best forum for this, but I thought I'd give it a shot since I've received a lot of help here before.

Anyway, I was loading Windows XP onto an older machine that had Vista pre-installed. I shrunk the Vista volume down and loaded XP. Everything seemed to be going well. I finally got it installed and booted (XP), however none of my hardware was being recognized. After some research I found that it was likely because XP didn't have the drivers for my motherboard. I started moving those drivers onto the pc and began installing. Things started working, including network adapters and my video card was finally being recognized. However, I noticed that one of the drivers was "updating" the BIOS, but I panicked because the version number was actually lower so I tried to cancel. Well I was apparently too late, and when I went to restart the computer, it no longer boots up at all. The light on my tower stays yellow, instead of turning blue when it boots. I am using a Dell Inspiron 531.

My goal was to have a machine with XP installed so I could just use it out of convenience for some older PC games that I have, but I am having quite a bit of trouble. I also noticed that even though XP started recognizing my GPU, it wasn't labeled the same as what is actually on board. It has a GeForce 8600 GT, but it was reading something like 4600 or something. Any help or advice is appreciated, I'm rather new to this stuff. Thanks.

Why don't you just run on a virtual machine? (Oracle's VirtualBox for example) Much simpler and if you fuck up you can just delete the virtual machine.

However I would recommend reboot the whole computer since you clearly have fucked something up.

If you aren't able to desolder and replace the BIOS flash chip with a properly flashed one, you may need to replace the motherboard. More info here:
http://en.community.dell.com/support-forums/desktop/f/3514/t/19296790

Also, small piece of advise for your next attempt at dual booting. Install the OS from older to newer, since it's more likely to properly understand the boot sector.

Most likely your BIOS is now broken. I read in computer magazines that it can be repaired, although it is expensive. If it is an older PC (I guess so, because Vista) it may be favorable to replace it complete. I think the best idea is to go to a computer store and ask for the cost of both.

Rule #1 of computers, don't f*ck with things you don't understand.
Do not touch your BIOS unless you're absolutely certain you need to.

You could try clearing the CMOS, it probably won't help but at least it won't hurt and is relatively easy to do.

Misflashing bios is not a hopeless issue. Motherboards usually have a backup system for that occasion. As Smannesman said - disconnect a PC from power grid, remove battery from its socket on the motherboard for 5 min, then put it in place and try reboot PC. If it doesn't help try to find manual for your motherboard because there is is a chance that you will have to play with jumpers to repair your PC.

EDIT:
Here's a manual for Dell INSPIRON 531S. Follow this chapter and there's a good chance you'll be on line soon
http://www.manualslib.com/manual/36565/Dell-Inspiron-531s.html?page=177

A driver shouldn't update your BIOS. That's a separate update all on its own and nothing to dow ith drivers. I wonder if you grabbed the wrong update file... Regardless, try resetting the CMOS, as noted. If that doesn't work, try contacting Dell. Even if your rig is out of warranty, they may be able to suggest a fix for it.

I just took the files that were listed for my motherboard and started installing them, it was stupid to assume that they were all necessary. I didn't mean to do anything with the BIOS, I just caught it when it was updating, but it was too late.

Thanks. I'm hoping that removing the battery and reinserting will fix the issue. I should have been more cautious with which update files I took. As far as "downgrading" a BIOS, I have no clue, but that is what seemed to be happening, and it seemed to be working before I canceled it. So maybe it just completely rewrites it? The reason I didn't just use a driver finder program was because I was using XP and none of the browsers were working anymore, so I couldn't really use anything from the Internet.

Hopefully it's not too late for that motherboard, but keep in mind that Dell does a decent job having drivers on hand for even older machines. They may not have every latest and greatest driver, but they'll typically have relevant BIOS and chipset updates available, which are some of the more important ones.

For general updating, I've had good results on a few different machines using SlimDrivers.

Best of luck with it.

Quite many PC vendors seem to include BIOS update files to their "drivers", e.g. for my ASUS G75VW laptop:

http://www.asus.com/ROG-Republic-Of-Gamers/G75VW/HelpDesk_Download/

The BIOS update file is there in the "Drivers & Tools" section, along with all the driver updates. However, that's the BIOS binary only, you need to use a separate tool (WinFlash) or use it from within UEFI/BIOS to actually update it.

I first encountered those updates with Dell, although these days many vendors supply them.
It might be because you used to have to boot with a special update disk to flash the BIOS, but these days the installer can be run from Windows.
And yes it is totally possible to flash an older version, it would depend on the installer of course whether or not it would allow you to. But I think they commonly just warn you and don't prevent you from flashing the incorrect version.

That always puzzles me. Do PCs have backup banks for e.g. the BIOS or not?

As part of my earlier work, I've been working with all kinds of BIOSes, UEFIs, firmwares etc. on hardware that is not exactly PC hardware, but using same components (Intel CPUs, BIOS, UEFI etc.). I've done BIOS updates probably hundreds (or thousands, lost count at some point) of times, created scripts that update them etc.

At least on those systems e.g. BIOS update seems pretty much foolproof, the user can't brick the unit with a failed BIOS update even if he tried. If I've ever had a failed BIOS update for some reason, at worst I've just had to run the update again, that's all.

How it works is that the BIOS has two banks, active and backup. As the name suggests, the active bank is the one running. When you perform the BIOS update, it is actually the inactive backup bank that is being updated. Only if that backup bank update was successful and the checksum matches, that bank is made active (and the bank which was earlier active becomes the backup bank).

So, if the user e.g. interrupts the BIOS update or there is a power outage during the flashing or whatever, it just means the backup bank is corrupted. It should not affect the system at all, because the active bank is still intact. Then all you need to do is to run the update again overwriting the corrupted backup bank, until the flashing is completed successfully. Then the updated backup bank will become active, only then.

So all in all, I am quite puzzled by these stories how PCs get bricked left and right by corrupted BIOS updates. Either it is really true that PC BIOSes are so poorly designed that they have only one bank (I wonder how many cents is being saved there?), or then it is something else, e.g. the updated BIOS is in default values and that is causing some problem to the system. (As a sidenote, I've also updated my various home PCs and laptop BIOSes countless times too, and never having problems there either. Lucky or not, I don't know.).

To the claims that one should not try to update PC BIOS unless necessary: at the same time people don't seem to have any issue reflashing their smartphone firmwares whenever the vendor releases an update for them (I've e.g. updated one Samsung phone firmware probably five times already). Isn't updating your smartphone firmware just as risky as updating the PC BIOS?

How about gaming consoles, I think they get firmware updates, even forced ones, every now and then. Risky or not, should those updates be avoided?