I think my mobo is screwed but not 100% sure,
What happened was I came to put in a new HDD and I did a bit of cleaning inside and screwed somethings in that should have been done a while back. When I came to turn it on two of the fans span for a second and then went straight off with no power. So I did a lot of messing around by taking out various components like the hdd i put it, cd rom, ect. and some how it started to turn on all the time so I started putting things in one by one and the first thing i tried to put in was the same hdd and went off again so I disconnected it again and still it span for a second and that was it. but I went back to try it and it worked apart from nothing would show up on screen, but I could hear/see the fans moving. so i tried the hdd once more and it started again.
Now it seems I can put everything back in and it will still power everything but nothing will show up on screen and then after about 30 secs a big long beep started going. at first I thought it was the battery on the mobo so I changed it and still the same result, I even thought it was the onboard video card so i tried putting in my gfx card and worked fine, so I ruled out the on board graphics and the psu as if the psu wasn't giving out enough power as it wouldn't of powered my gpu. while doing all this the beep carried on.
my rig: Foxconn M7VMX Series|Intel Core 2 Duo E7200GHz|2.00GB of RAM|500GB Western Digital SATA HDD|500GB Hitachi SATA|500GB Maxtor External|Nvidia GeForce 8 Serise 512MB.|400W power supply.|Windows Vista Ultimate|19" HD Monitor