I have a Dell 435MT i7 w/ 64bit Vista, 3 years old.
About 3 weeks ago we had a power surge and my computer attached to a surge strip shut down. Pressing the power button it would not restart. I unplugged the computer and before I opened it to reseat some components I decided to plug it back in instead. It worked fine powered on for 7 days. Then I manually shut it down after a week, unplugged it and left for vacation.
I came home, plugged it back in and nothing. Green light on the p/s and orange steady light on the mobo, however I reseated the vid card and memory. Still nothing.
I found another forum which showed many others with this exact problem on the Dell 435MT, they had no firm conclusion but for the heavy majority a new P/S solved their issue (there was specualation on firmware issues with a power outtage). I purchased a new Corsair CX500, installed it, and it turned on.
Figuring I was home free, big mistake. When trying to boot Vista theres a split second blue screen with wording at the top, far to fast to view with the naked eye. It immediately shoots me to System repair. I ran the memory and disk scanning segments as well as general diagnostics tools, including confidence test and all passed.
Previous to installing the new P/S. I did reseat the cmos battery and jumper (to same position) so I wonder if this messes something up. Power seems good, cd and dvr drives open/close. mouse/keyboard function is there. No funny sounds, no beeps.
I do have a factory installed raid 1 setup on dual 600gb hd's. Again, wonder if something at play there. Video card is a 4850 512mb.
I no longer need the redundancy of the raid setup. But a clean install is the furthest thing on my mind.
If reseting the BIOS put you out of raid mode then you'd have a problem. verify the SATA controller is still raid mode.
Download and run a bootable diagnostic. (e.g. google "ultimate boot disk") Dell should also have a downloadable diagnostic. Goal is to see if memory or something else flaked out when the PSU went. IF the diagnostic boots cleanly and the SATA controller is correct then see if your bootable diagnostic can read the windows disk. If so you may be able to rebuild your window install w/o losing data.
Post when you've tried a few of the above (or whatever you end up trying) good luck.