I'm running Vista Home Premium on a Compaq C700. Anytime I turn on the machine and open an application, it freezes and I have to power it down. This happens, for example opening IE, I also opend Control Panel and clicked on System Maintenance and it did it again.

Any suggestions?

You may have to reformat your PC I think. I hate saying that because I myself have had issues and had to do it which takes forever! It did work for me though!

How much RAM does the computer have?
Hard drive size? CPU speed?