Since 2 weeks, i have randomly a high cpu usage, even when I am not using the computer. After 2-3 minutes its over, but while the computer is doing SOMETHING, i can't really do anything with it... Is this a virus? I am using Windows XP, and have a router firewall.
please check your system for strange software that is running in the background, like spyware or adware. You find programs like the Google-Pack, Ad-Aware and Hijackthis here: