Whenever I have a program that needs to reboot or even if I manually reboot from the Start menu, my computer stays on. It'll go past the "Saving settings, etc" stuff and then the monitor goes blank but I can still hear my fan running and I can feel the wind blowing out from the tower case. I know the computer stays on when it's rebooting but mine doesnt turn off nor does it even boot up again. It just stays at the black screen, monitor displaying nothing. Any ideas?

We need some more information about your computer to look into it:
full system specs:
computer make/model
OS version
Total memory installed "system ram" and what memory slots the ram is installed in
Graphics adapter make/model and driver version
Monitor make/model
Peripherals "mouse keyboard joystick USB devices etc.. need all the makes/models for those..

Also have you updated any drivers recently before this started?

I think the most recent driver I installed before this occurred before all this happened was drivers for my Zen Vision W but the problem didn't occur until a few bootups afterwards.

Specs:
Windows XP SP3
3x1GB ram, only have 3 slots; 1gb sticks each
GeForce 8800 GT
Monitor is acer, don't know model but it's a flat type and has no flaws while system is running
Using:
- Cyborg Keyboard
- Razer Diamondback 3G mouse
- Belkin 7-port hub
- Creative Optia Webcam
- Linksys Wireless-G USB adapter

ah xp sp3 has a few shutdown issues with 3rd party software..

Do you have Iolo brand firewall?

Quick test to see if it's a driver/software issue; power up the sytem from a full power off state; boot into safe mode, "this disables all the extra startup files" once safemode has booted go to the start menu and select "shut down" see if it will do it... If it does; could be that one of your applications or drivers are hanging up the shutdown process..

There's a procedure to test which startup item is causing the hangup. If it's a startup item issue "found out by successful shutdown from safemode; can you get a screenshot of MSconfig "startup" entries "from normal boot mode" and post a .jpg of the screeny? Then I could suggest which startup entries to temporarily disable.. The procedure is to open MSCONFIG and disable/apply one change at a time; noting which startup entry was disabled; then restarting, and testing start/shutdown/restart, to see if it resolves the shutdown issue.