I am new to this forum but so far I have found it to be helpful to users. Just recently, My unit has been attacked with viruses and Trojans, thanks to my younger brother who keeps plugging his MP4 player to it without my knowledge. I tried cleaning the virus through my anti virus program, but i am sure something has managed to proliferate. I know this because some pop-ups keep on showing on, and command prompt automatically runs every 10 minutes or so. I ignored them, thinking that maybe those "signs" will just vanish, till one day my pc stopped suddenly, I restarted it, but since then it always fails to boot. I get this message every time I try to run it - "CMOS checksum bad".I tried the "CMOS battery thing" but it has not worked out fine for me. Can anyone give me a hint on how to deal with this problem? And what is the real problem anyway? Thanks!