Windows hangs during shutdown/restart/sleep

About half the time I try to turn off the computer, restart, or enter sleep mode the computer freezes up. I get the 'windows is shutting down' screen or equivalent and it never actually resets, sleeps, or gets to the 'it is safe to turn off the computer' screen. Any ideas what this is about or how to fix it?

Here are some of my specs:
Windows XP Home Edition
Dolby Digital Certified 5.1 (6 Channel) Surround Sound Card
128MB GeForce3 Titanium-200 Video Card
ASUS A7N266-C Motherboard AGP4X / 266 MHz bus
256 MB DDR SDRAM (PC2100 266MHz) 1.5GB Max
40GB IBM 7200 RPM Ultra ATA/100 Hard Drive
CasEdge Mid-Tower Case / 300 Watt ATX Power Supply
I think my processor is one step above the 1900PR AMD Athlon XP

 

It could really be anything.

Have a look HERE and HERE.

 

I formatted my hard drive and that cleared up the problem.

 

Yeah, formatting will always do it!