Hi:
The processor yu want to buy for your dc7100 SFF will absolutely not work.
Below is the link to the quickspecs for your model. See page 5 for the list of supported processors.
Only the Pentium 4 processors listed will work and I do not recommend upgrading past the Pentium 4 650 due to the excess heat that will be generated by the higher wattage processors.
http://h18000.www1.hp.com/products/quickspecs/11948_div/11948_div.PDF