Thanks for the idea Scat. I will test and replace the CMOS battery and see what happens. I was wondering about whether the CMOS memory would hold configuration type of information for the slots. From what I gathered... the issue with Windows "thinking" about some kind of corruption was after I re-seated the CMOS battery. It seemed that reseating the CMOS battery affected some settings, and Windows didn't like it. And "repairing" it caused me to shoot myself on the foot. Looking back, I should have tried starting up "like normal".
I looked around the BIOS menus with every option 3 times. I couldnt find anything related to the PCIe Xxxx slot settings at all. Next opportunity I shut down and open up the box, I will double check the power cables feeding the PCI bus to see if there is any loose contacts.
Yes, battery powers a chip which holds some configurations... not sure whether it holds optional PCIE slot activations. I was thinking that the CMOS battery could be weak and caused the setup to revert to "default".... which may be "slots 1 & 2 enabled"... and you might need to enable the others by selection. (?) Doesn't seem all that likely, but in troubleshooting you need to keep trying things until you find it. May not be the case with your situation, but I've learned that whenever the system seems to be squirrely/intermittent, "check the battery and check the RAM".
A couple of things I've noticed: 1. Do/did you have any AV software installed before/after the cards stopped being recognized? 2. What was the patch level before/after? How about now with the reinstall? 3. Have you searched the card manufacturers site? Maybe there is a conflict with a recent patch. 4. Did you try all the slots with just 1 card, to make sure the slots are working? 5. What's the wattage of your PSU? Have you considered swapping it out for a new one to see if that is the problem? 6. Did you have an electrical storm just prior to the cards stopped working? Are you hooked up to a (good) UPS to even out the current? Are you the same guy that was having problems 6 months ago?
Thanks again for the additional suggestions Scat and blah12345678. An update: Problem now resolved I know you are all anxious to know what happened! LOL Scat was right on. It was the CMOS battery CR2032. I took out the old one. Voltage still measured 3.1V or so. I bought a new one today. Voltage measured as 3.3V. Plugged in the new one. Installed the second EVGA 8400 GS card. Started up the system. Voila! Windows said "installing new driver". Screens blacked out... and then... 4 monitors got lights! I had also reviewed the Xpower motherboard user manual. Apparently they have some slot population rules. For 1 PCIe X16 card, you put it in what they labeled as E2. (E1 is actually a PCIe X1 slot, which I don't use. It is so small, I missed counting it.) For 2 cards, E2 and E5. For 4 cards, E2-E4-E5-E6. For 2 years I have been using E2-E3-E4-E5. As it turned out, it didn't seem to matter. Tonight I had tested both configurations and everything seemed to work just fine either way. But I will stick with the manufacturer's specifications. Maybe it's for better heat dissipation, better power manager, whatever. I think I had read somewhere about the motherboard scanning the hardware cards in those slots, and prep the information for Windows' plug-and-play. (But I couldn't find that webpage again.) That seems to make sense. CMOS power loss, configuration not savable with each boot. Windows doesn't see the additional cards, and thus not load the proper drivers. Looking back... I should have changed out that suspected problem battery first before resolving to re-install Windows (even did that a couple of times). Time wasted for no gain. Just $1.99, would have saved me a whole afternoon and evening, not to mention a few hairs. So... Thank you everyone trying to help me resolve this issue, especially Scat! Your kindness are much appreciated! And blah12345678: I don't have any AV software on this box. It is one of my 3 workhorse computers. I only use them for TradeStation plotting charts. I don't use them for anything else. They are to be on 24x7. I don't even want to reboot them unless I absolutely have to. My record is on this very box - it had a continuous up time of 121 days running TradeStation 9.1. I don't bother with applying Windows updates nor driver updates. Whatever worked when I first installed everything 2 years ago, I want to keep it that way. Power of the PSU is not a problem. I purposely oversized it. I have a 630W PS. I have only 4 dingy little 8400 GS cards and 1 disk drive inside. I don't have a UPS. Not a mission-critical box. And the electrical storm incident... it wasn't me. Thank you for all your ideas. Now I have 8 monitors back to work. And actually I got 2 more using 2 x USB-to-VGA adapters. For a total of 10 monitors on the same system. I had tried running a fifth 8400 GS card on the box 2 years ago. For whatever reason, that configuration never worked. Computer froze up, crazy screen displays, something of that nature. So drivng the 2 extra monitors via USB is fine for me. Unfortunately Windows 7 only handles a max of 10 and I don't have special software. I settled at 10.
One can see where those population rules could make some sense for air flow/cooling. And I guess there would be no need to save the video card configuration at power down as you might change it (add or remove cards) before next power up.
That is one thing I couldn't figure out. I can only speculate that the BIOS stores the configuration information (during hardware start-up sequence) in the memory powered by the onboard CR2032 battery. When Windows starts up, with the plug-n-play feature, Windows makes BIOS calls to inquire about the hardware info. BIOS answers based on what it stores in its memory area. Once the CR2032 no longer functions, nothing is stored in those memories, and thus Windows perceives that no device is present.
Troubleshooting can be very annoying. I recall once when the Dell tech was sure "it was RAM"... sent me out replacements. Wasn't. 'Twas the little battery. Another was especially bad... Dell diagnostics first runs RAM test. Said mine was OK. So, started looking elsewhere... EVERYWHERE. I replaced all the drives, video cards, cables, battery, PSU... everything except the CPU and the RAM which had already tested as OK. Turns out, it WAS the RAM... in spite of the diag report.
Indeed trouble-shooting can be hard. We can only do our best to co-relate all the observations and seemingly cause-and-effect. Often times, problems are compounded and the real cause is not straight-forward to see. We have to do systematic tests, make hypothesis, collect evidence to support or disprove such hypothesis to hopefully nail down the real culprit. Truly systematic diagnosis is very time-consuming. With experiences, though, we can typically take a heuristic approach and make some good guesses on where to start to speed things up. I wish trading is as easy.... LOL