BIOS Problem

Hello,
I have forgot my windows xp password, I was told to take off the CMOS battery and leave it out for couple of hours after installing the battery back in I powered my PC nothing seem to happen the screen was blank no boot-up sound even the cd drive would not open I tried ON/OFF couple of times but nothing happened the PC would not boot-up to bios or cmos setting as it use to come with logo at the beginning. I have told that my motherboard could be faulty but not guaranteed, I have got my hard drive checked its ok, it has been formatted with fresh windows installed. The hard drive was taken out from my PC and was installed from a different PC. Some how the PC would not load anything on the screen its all blank even with hard drive formatted, I've tried clicking some of the keys from the keyboard no response. If anyone thinks they know how to fix this problem or have any idea please help me I will really appreciate your help thanks.