After replacing the cpu, I received a BOOT FAILURE::SYSTEM HALTED message. My hard drive and CD reader are no longer being detected. When I insert a bootable floppy, the system will boot from the floppy. I believe that I damaged the IDE controller on the motherboard. If I install an IDE controller PCI card and disable (via BIOS) the IDE on the motherboard, is there a chance/way to boot from the IDE PCI card? Or is my system now just a big paperweight?

I highly doubt you damaged the IDE controller unless you opened the case & just started ripping & tearing things out. Are you 100% sure the CPU is compatible? Did you reset the BIOS using the clearCMOS jumper?

i kind of agree with jam about the likelihood of damage to ide, but i have had a dell optiplex gx260 where both IDE channels just stopped working with no sign of physical damage and the BIOS settings being fine and swapping every single component with a working gx260 one by one did not fix it so it was firmly established as mobo problem

"I believe that I damaged the IDE controller on the motherboard. " That's extremely unlikely if it was working before you changed the cpu. I have NEVER come across one that actually was, unless the mboard was damaged. What were you attempting to do? Were you having problems you thought replacing the cpu should fix, or were you trying to upgrade the cpu? If you were trying to upgrade the cpu, the cpu has to be compatible with what the mboard supports and be one the mboard bios can detect - if it isn't your mboard may not boot normally. If you replaced the cpu because the mboard was not booting, that probably is NOT why the mboard was not booting. If you still have the cpu that was in it before, try installing that. The Dell Dimension 4600 has a reputation of having a power supply that is more likely to fail, and it often damages the mboard while failing. That may apply to your model too. Did the power supply fail and you replaced it? The effects of any damage done sometimes don't show up right away. Failing power supplies are common and can cause your symptoms. Check your PS. See response 4 in this: http://www.computing.net/hardware/w... ..... If the PS seems to be fine (the only way to tell for sure is to try it with another working computer) ....... Open up your case and examine the mboard to see if you have bad capacitors, and/or other findable signs of mboard damage . This was the original bad capacitor problem - has some example pictures. History of why the exploding capacitors and which mboard makers were affected: http://members.datafast.net.au/~dft... What to look for, mboard symptoms, example pictures: http://www.badcaps.net/pages.php?vid=5 Home page that site - what the problem is caused by - he says there are STILL bad capacitors on more recent mboards. http://www.badcaps.net/ Pictures of blown capacitors, other components, power supplies, Athlon cpu's, etc.: http://www.halfdone.com/Personal/Jo...

Check the cables to verify they are fully seated on both ends. Both power and data.

Removed new processor. Installed the previous processor. The system now boots successfully. New processor is possibly not fully compatible and/or defective. Done. I should have done this swap before posting this problem - common sense. Thanks for the replies!

We're glad to hear you solved the problem. Dell didn't make the mboard. If the make and model of it isn't obvious when you examine the mboard, if you search the web using something such as: Dimension 4400 motherboard you may find info that tells you who actually made the mboard and what the model is. If you do find that, see if there's a cpu compatibilty list for the model. On the other hand if it isn't a socket circuits or cpu core voltage incompatibilty problem or similar, you aren't likely to find out what any Dell bios version supports regarding cpus for it. The only thing you can be fairly sure of is there are probably other Dell models that use exactly same mboard and some of them may have faster cpus installed - those cpus should work fine. If you search the web using the Dell part number for the mboard, you may find info that tells you which other Dell models the mboard was used in, and with that info you can look up which cpus they have. If the cpu is on the actual manufactuer's cpu compatibilty list, you could in theory flash the bios with the actual manufacturer's version that supports that cpu, but if you did that you might not be able to use the Dell Recovery CD or CD set - the program may quit when it doesn't find a Dell bios version.