A few great system utilities ...

Currently Listening to =>Jane's addiction - Just because
Now, this is fun for retreiving all kinds of password recovery and other related hacking stuff. A lot of other utilities also there.
The Best 46 freeware utilities of all time . Now this IS good stuff.
More fun utilities here including FTP Wanderer, a real good FTP Manager.
Another great list of utilities for WinXP
Oh and MUST include this - 99 Performance Tips for Windows XP. An awesome way to improve system performance and retrieve lost disc space.

Disclaimer: Like some of you might notice, a couple of the above were taken from Sheng's site

Edit: Ermm this isn't exactly a great system utility, but if you wanna download game demos, this is the place to do so!
And this is for you guys who think I play too much and not work :P
Thats it. MUST work now ...