Hp a330n black screen problem

Hello,

I have an Hp pavilion a330n, for some time my computer has been changing the date and time back to 2001, I am running windows xp, I have talk to people frm microsoft they said that it was a problem with the mother board batery. The computer worked fine when I change the date and time to the correct date, but two weeks ago only a black screen is comming up is not booting to when o hit the F1 key to allow me see the cmos settings, so I replace the battery since then with no lack. The fans are working the HD are running, I remove the add. video card and plug the monitor in the mother board video socket nut no luck. Could some one please shine some light in how to solve this problem with my computer?