I hate dealing with Dell OEM. Lee2010 does the board look like this?http://en.wikipedia.org/wiki/Socket_478
Or like this?http://en.wikipedia.org/wiki/LGA_775
If the pins are raised on the motherboard it is LGA775. If it has holes it is Socket 478. With Socket 478 you would use the Pentium 4 that says Socket 478. With LGA775 you can use Pentium 4 5xx and 6xx series and Pentuim D 8xx and 9xx series CPUs. All of the above are hopelessly outdated.