Motherboards keep failing? - refuses to post and no video
I built my own computer and all worked fine for nine months. Then suddenly my computer failed to post and I had no video. I messed around moving memory chips and removing components and resetting the CMOS. Eventually it started working again but I had to limit the processor bus speed to 133mhz (It's an Athlon XP3000+ so should be set to 166mhz).
After a couple of days it failed again and screen just said BIOS Checksum error. I read on the internet that the ASUS A7N8X-X motherboard is prone to this so I bought a new one. (An ABIT motherboard).
All worked fine for a few hours last night. I decided to reinstall windows and it froze twice. The second time I tried to reboot and it won't post again and I have no video. Can somebody PLEASE PLEASE PLEASE give me some idea of what could be wrong? I've replaced other components so all that's left is the graphics card (ASUS FX5600 i think), processor, and memory.
Thanks in advance,