The last two times I shut my computer down it froze during the shutdown process.  Now it won't start back up.  It's giving me the diagnostics numbers 2 and 4, which signals  graphics card failure, so i TOOK my graphics card (Nvidia geforce 8600 GT) out to look at and two of the capacitors have large cracks in the top of them.  i took the card out and tried to use my integrated card, but it gives me the same diagnostic lights.  i tried putting my old ATI radeon card in, and then it gives me lights 1,3,4, which the manual doesn't list as a combination, and the computer shuts down and restarts every ten seconds or so.  took the radeon card out, and it gives me 2 and 4.  ANYONE have any ideas about what could be causing this??Unfortunately that card may have taken the board out with it...
CHECK for similar looking capacitors on the MBoard itself...if you SEE any looking like that the board will need replaced....or if anyone in your area works at board level you could gamble on having the bad caps replaced.