I believe you might probably be overwelmed by spyware and/or viruses. You should first try to lighten your PC a little bit, go to Start->Run and type msconfig. Then go to the Startup part and uncheck everything that looks like not useful (you can always enable them again). Then restart, now it should be a little less stalling... Next step is to run some good antivirus and anti spyware apps.
If you have already done all this and it doesn't seem to help, then you might need to give us more info on the changes you made to your PC before it started jamming...
For some reason, the following programs will not open:
or any other program
I am also have difficulty updating to SP 2
I am running Windows XP pro
My computer is stalling and jamming all of a sudden....nothing works
Please help me