This is a tricky one...

My system has been running about a year and a half now (24/7 excluding a couple of breaks). I had some weird hangs for a while. Now the computer refuses to start up. Sometimes it does however start and stay running for a couple of hours. There is absolutely no trace of any failure in the logs. Voltages are OK one second before hanging.

First only the graphics failed. I still could log on to the machine from outside. Then I removed the graphics card. But still the system hangs after some time.

When the computer doesn't start up the following happens:
PSU and CPU fans spin, HDD does not spin, no output to display (if graphics card connected).

Heat is not an issue.

MB Epox 8KMM3I
CPU 1800 Duron Applebred

Any suggestions? Please? Help? Anyone?

sounds like a bad hard drive to me

...

You can stick a frog into the ide connector and still get into BIOS. HDD works fine.

That's your problem -- you have a frog inside your computer! Just kidding, LOL.

Just a wild guess, did you check your CMOS battery? It could be low in juice. If that's not the case, and since your machine is running 24/7 year round, I think you mobo's starting to go.

I would test a new PSU, my PC started to do the same thing, faulty molex connectors everywhere and just a crap PSU...new PSU, no problems!!