Malware or Hardware Problem?

Hello all : )

My computer randomly freezes and occasionally restarts itself. I have Norton but have not been able to finish a scan without it freezing. Most recently my wallpaper changed on its own to red and white. It is also a Compaq so all of the system info is saved together on one recovery disc rather than having seperate installations. Most problems with freezing occur while using the internet but are not limited to internet use. If anyone can suggest anything for this problem it would be greatfully appreciated.

Thanks,
LinvasionZ