Computer shutting down

System shutting down after being on for 10 to 15 minutes.
Sometimes it will shut down before getting to the login screen.
Sometimes it doesn't shut down at all.
REALLY CONFUSING.

Actually it really doesn't totall turn off as the light still illuminates on the power button. To completely shut it off I have to hold the power button for several seconds then it shuts down.

Platform: Windows XP SP3 (WinNT 5.01.2600)
MSIE: Internet Explorer v7.00 (7.00.6000.16735)


Ran hijackthis and have attached the log.

Ran Malwarebytes' Anti-Malware and got zero negative results.

Yesterday I did three things which I usually don't do.
1. I deleted three folders found on my C: drive.
The folders were huge and contained, what appeared to be, left-over files from surfing the web. The file names were nonsensical, like: d9161a3ef816ed30c32f (this is an example the file name and not the real file name.)
But the system ran fine for hours after I did that so I'm not 100% sure the problem started there but there could have been a file in one of those folders that is needed... I don't know.

2. I watched a video a friend of mine sent me. The file name is PolishPolarBearClub.wmv. Again, no problems after watching the video (not worth watching by the way... stupid) but now my system is shutting down and I can't figure out why.

3. I stopped several prorams from launching at startup. Here are the programs I removed from the startup process:

ICQ.exe
Acrotray.exe
Reader_ls.exe
Applesyncnotifier.exe
hpwuschd2.exe
ituneshelper.exe
qttask.exe
SC_ACR~1.exe
hpqtra08.exe
hpqthb08.exe

Thanks in advance.
GV