OK I know this is a thousand year old question but this is unique in the way it pops out..
So here it goes,
My specs first,
1) Epox 9NPA Ultra+ Mobo
2) Athlon XP 3500+ CPU
3) 1 GB RAM
4) 8800 GTS video card
5) 400 W Silverpower PSU
First time I had the no-signal problem was, after a power outage while watching a movie. Power went off and then I waited for it to come back (There was a spike in the power while I was waiting for the it to come back on btw and power went off instantly again, just to note), when the power came back on I powered on the PC and continued with no probs.( Tomorrow morning, when I turned on the PC the monitor would get no signal at all no matter what I did. But the PC booted and the hard disk loaded the OS. Just no signal from the video card at all.. So I tried everything including;
1) Removing power cable and pressing on button for 30 secs
2) Resetting the BIOS and removing the CMOS battery
3) Removing/moving the RAMs
4) Pulling all the connections out 1 by 1 and try powering on
5) Trying other PSUs to see if the PSU was faulty
But nothing worked so I took it to a service and they told me that my video card (6600 GT back then) was *kind of* faulty meaning it would not work on my PC but it would work on other PCs (?!?) and told me that while it worked on other PCs, it wouldnt mean that it was functional and that it may do the same in other PCs sometime later and advised me to get a new card (because they had tested another PCI-e card on my PC and display was on meaning there was no problems with the PCI-e slot either - I guess-) So I did get a second hand 8800 GTS, plugged it in and voila! It worked without any problems at all.
Then I used the computer for about 2 months UNTIL yesterday where it started to do the same problem out of nowhere (no power outages, no nothing..) No video signal to the computer at all.. I had the old card (6660 GT) lying around so I plugged it in to try it out. It didn't work naturally but the monitor light would turn green for 1-2 seconds before well.. Displaying nothing at all lol.. Then the light would turn yellow. After the second try, it doesnt even do that.
So yeah... This is the problem.. 2 cards and no video signal at all. I dont know how this might help but a couple of thing I noticed this time
1) The PC boots while there is no signal, but I have to press enter at some point for it to continue loading from the Hard drive. Since theres no signal I cant see if theres any message of course.
2) When the PC is booting first the USB mouse and keyboard powers on but after a while their lights goes off and doesnt come back. I dont remember getting this problem first time with the older case.
3) Epox mobo has an on-board diagnostic LED which shows FF (fully functional) after the boot and also it has 3 blue LEDs near RAM slots, CPU and another part I cant remember right now. But they all do light up indicating that there's no problem with those parts either.
While I havent had the chance to try the 8800 GTS with another computer to see if it worked, Im guessing it might since this was the case the first time this problem occured.
This time I cant suspect anything. I mean I am left w/o any thoughts as to what might be wrong, I've tried everything to no avail... It may be the video card, the PCI-e slot, the ram etc etc... I mean what are the odds of this problem happening the second time (I haven't even touched the computer after I plugged the new video card) I cant still pinpoint the problem and I dont have the funds to replace any components anymore. So I'm practically helpless at this point and need my PC for my work.. I would greatly appreciate any comments about this problem. Thank you..