I am running Windows XP on a 2GHz Pentium 4. My current video card is NVidia MX420 AGP. I am trying to upgrade to an ATI Radeon 9550 AGP.

I uninstalled the old card's drivers, updated the motherboard's drivers and then removed the old card. I installed the new one, turned on the computer and I get nothing. The pc starts up but there are no beeps. The monitor does not come out of standby mode and it seems that the pc is not detecting the new card at all.

Anyone know what the problem might be?

Will the system "come back" if you reinstall the old card?

Are you sure your video (AGP) slot supports the new card? (Voltages, etc) There are some minute differences in the contacts of various AGP cards.