No boot, post beep or MOBO LED

G'day.
Dismantled PC (removed peripherals and power) for about a month due to house renovations. :cry
Re-mantled it (?) and it won't boot. :cry
Power LED and HDD LED on front come on, but no POST beep, and no signal to monitor. No LED on motherboard lighting up. Pretty sure it has one. Power supply and CPU fans run ok.
Removed the following: two graphics cards (running two monitors, and onboard graphics is shot - I've run it like this for more than a year), HDD, RAM, DVD reader, floppy reader, all USB items, monitor, mouse, keyboard. No beeps at any stage.
Removed CMOS battery and tested voltage - very low. Tried a new battery and no change - no beeps. :cry
Left battery out for about half an hour then replaced it - no change.
Removed battery and for about 20 seconds shifted a jumper which I think is the one that resets the CMOS (no label). Replaced jumper, and still no change.
Any ideas? :confused
I'm thinking that the motherboard my have died, but I can't see why dismantling the PC for a month would do that.
What if the CMOS battery was too flat (lacking power) to keep things going. Would that cause this behaviour?
Maybe I should put one of the graphics cards back in. I have one AGP and one PCI. BIOS was set to run the PCI first, I think. It wouldn't work the other way.

The MB is Sapphire Axion RS300 (pretty old).
MB chipset is ATI Radeon 9100 IGP.

Merci d'avance.

 

Did you attach the 4 pin power connector to the Motherboard for the CPU if it has one?

http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems

 

Okay,
I did not pay attention to your post number, so I am pretty sure the question I asked was kind of dumb. :-o

 

It doesn't have one. Thanks for having a look, anyway. tgell.

 

I do not know the exact model number but are you sure there is not a connector? In the image of the motherboard here, notice the white 4pin connector just to the upper left of the CPU socket.

http://www.motherboard.cz/mb/pcpartner/RS300 AS4-A38.htm

 

On second thoughts, it does have one - hidden behind the power supply. :-o Just in the process of dismantling the whole thing to see if a good clean makes any difference.

 

all cleaned up but still not working.

 

Try this. Unplug power to the computer. Press the power button down for 30 seconds. Replug the computer and press the power button.

 

Basically, the same idea as tgell just gave but try starting with no CMOS battery--try a few times, unplug HD and CDROM too in subsequent attempts. Then again with the CMOS battery installed. Then again without it. (I'm only talking about spending maybe 5 minutes playing around with the battery. No wait periods or anything but do unplug the machine when putting battery in or out. I've found playing with the CMOS battery useful when taking a machine out of storage.) I realize you replaced the battery which should have se things straight but I would take it in and out anyway.

 

Thanks tgell and sach2. I had tried tgell's and I did try sach2's, but in vain.
I did eventually figure it out though. Bit of a long story, but it was to do with having it set up for two monitors, and only running one, and having the onboard video card cactus (which it was for some time, but it seems to have deteriorated further). I wasn't using the onboard; I was using AGP, but I had to have a working video card in a PCI slot before it would boot - that seems to override the non-functioning onboard video. Does this make any sense?:confused
I think I had come close to this a couple of years ago (and put in a PCI card), but forgot all about it:zzz... until one day the penny finally dropped.:-o
All good now. Thanks for taking the time out to suggest.:wave
P.S. No mobo light. There is what looks like an LED there, but it's not lighting up.