Another problem from a software noob.
Since a few days, my computer will slow down for no reason (no programs or processes running except the most basic from windows xp) and the cpu speed is reported as 884 MHz instead of 2.40 GHz.
I have to reboot several times before it goes back to normal.
I've tested my machine with three different antivirus programs (NOD 32, AČ and Ewido security suite) and several anti-spyware programs as well. All of them find nothing.
I've even formated and reinstalled windoze twice.
My specs: Win XP Pro SP1
Intel Pentium 4 2.40 GHz
512 mb ram