Hello all,
My daughter's dimension 4600, had worked for 3 years without a problem, then one day it just would not boot up. After a lot time reading advices on forums I removed the nvidea FX 5200 and tried to boot again.It will boot and I have to go into Safe Mode, however the screen is hard to read and sometimes the computer will not load my keyboard. So I purchased another Nvidea, same model, downloaded the new driver and fixes vrom their website. Well, that did not solve the problem. Of course I even tried Dell support (why, I can't imagine). Was told that I needed a new motherboard? The diagnostic lights on the rear panel, are all green, although I have had times where one or two would go amber on me. Conclusion: I now have 2 video graphic cards and a computer that will not boot with it instaled. Please help.

Perhaps your power supply is failing.