then it sounds as if the BIOS is failing to get through it's checking process.
This would indicate a hardware, rather than a software problem. The history would also suggest this as well.
In the first instance I would try reseating memory... trying only one unit if there are currently more than one installed.
Can you see what is happening on screen during boot up as bios is checking? If you can I think this indicates Power Supply and CPU are functioning.
Sorry I can't offer more advice. (And I'm open to correction on what I have offered!)