I bought a video game over a service called Steam. The game was Garry's Mod. I was installing it, it was on for about an hour before it got to half way and I was doing work and talking to people since everything was stacked at the same time. I had on Internet Explorer and Skype. To give my computer an easier time, I turned off Explorer and then Skype. Then my XP (which I just got back from my repair guy) froze just as the latter was shutting down. I think the biggest mistake was choosing to hold down the power button and have it immediately shut down. I forgot you could make it shut down slowly by just pressing it once. Anyway, I turned it back on and now when I turn most applications on, it starts out slow then freezes after a minute or two and some things come on without my command so that means the computer has applications like Skype running that I can't stop.
A friend suggested I go to Task Manager and shut down the Steam.exe process, but the moment I pressed X on the Task Manager to turn it off, the whole computer froze except for the cursor again. I've done a few searches and some things have come close to this situation, but things like the computer model have been different. It's hard to access stuff in time to do anything with the computer. Because of stuff that comes on automatically like Skype, it just freezes completely without me even touching it. It could be stuff besides Skype that I don't know about too. I really need help with this.
Try starting it in safe mode and running your antivirus program from there. As the computer starts to boot start hitting the <F8> key and you will get options for starting windows. One of the options is Start Windows in Safe Mode. This will load the minimum drivers and apps and get windows up and running. Let us know what happens and we can work from there.