Even if the NVRAM settings were lost because of a dead battery and set back to their defaults the PC should still POST. OP, you may want to review this article to see if any of the symptoms listed exactly match what you are experiencing: http://www.informit.com/articles/article.asp?p=347825&seqNum=5
Sounds suspiciously like a bad power supply. You could get another one and replace that power supply and see if it works. If not, you know it isn't the power supply.