My preference goes to PerfectDisk...

I play around with different ones from time to time but honestly the windows one is fine for me.

Actually it's always the windows defrag API doing the work, the third party software simply instructs it to do it in different ways.

As someone else mentioned JKdefrag I seem to remember they have some really good FAQs about defragging on that site, definitely worth a look.

THIS.

I tried every free one I could get my hands on but in the end, meh. Windows defragger wins.

...tweak it.

Here is a recent test of defragging software:

http://www.computerbild.de/bestenlisten/Die-besten-Festplatten-Tools-3909936.html

its in german but you should be able to read the tables.

tl;dr edition: For Windows 7, the default defragger will do the job.

I'm afraid I haven't got the time to read the replies, but I can recommend Defraggler because I've been using it for years. Piriform's free software (also made Ccleaner, Recuva, Speccy, all great tools) has never let me down. I suppose it might not be the most advanced defragger but it'll do the job nicely.

If you are using Win7, you rarely will have to defrag as the OS automatically defrags when the system is Idle.

And if you have to defrag and are impatient, then just turn it on when you go to sleep or go out for an evening.

Been using Diskeeper 2010 and love it. Have set it to defrag in the background and havent had to worry about defrag at all.

XP's default defragger is just a crippled version of Diskeeper. I installed the full Diskeeper 9 on a system on which I had been using the default defragger, and it showed the drive was quite fragmented, whereas the stripped version reported it as clean.

For 1Tb hdd or bigger, no need to defrag, just make sure all partitions are NTFS file system

It's not so much black and white as this: I rarely use my XP rig anymore for anything other than surfing the net and a few older games that are already installed on it. Why bother installing a new defrag program when the one I have is doing just what it needs to do? My rig works fine with what I'm using and I don't find I have any issues with performance. In short, there just does not seem to be a compelling reason to bother.

Until it doesn't, JkDefrag isn't being patched as far as I know.

I ran a thorough defrag once using UltimateDefrag Free Edition.....NEVER AGAIN. It corrupted several OS directories when I run it before boot to defrag the OS/unmovable files as well. Had to reinstall windows.

EDIT: Just noticed that my pc has been defragging every week without me knowing. I wonder if that's why my old HDDs started corrupting after several months of use. Someone DID say a bit back that constant defragging ruins HDDs lifespans after all.

I shut the auto defrag off for now.....better to be safe than sorry.