I currently have a P4 model 521 processor. Do I need to stay in the 5x1 series or will I be able to use the 6x1 series. The 6x1's are still single core but have 2 MB of L2 Cache instead of the 1MB that the 5x1s have.
Check your cpu heatsink first. Those 2 meg cache old p4's run very warm. You may need to remove the old shroud around the cpu heatsink (if your dell case uses it) and install a p4 heatsink retention bracket, which goes for about $5. Personally, I don't recommend you spend any more money on it. It's not worth it.