BLACK SCREEN :(

Hi, I wiukd very much appreceiate some help. I will describe as best as I can my proble,/
Mother BoardMS-6541 Chipset Sis 745.
Board ran Athlon 1900 @ 1.2Ghz. Blower packed in, received a long series of bleeps.
Switched off. Fitted an Athlone 1700+Xp as this is rated at 1.475Ghz in place. Start up BLACK SCREEN, I had my XP Disc in the CD and it started to load that.As I didnt know what was going on had to switch off. Have reset BIOS no change. I dont get any BLEEPS.
There is a D Bracket fitted which has all 4 l.e.d’s on red. Due to the construction of the Athlone great care was taken in fitting the heatsink. IM AT A COMPLETE LOSS. Any assistance greatfully appreciated