Dell XPS R450 has a bios the limits what CPUs you can put in it because the voltage regulator on the motherboard has limited capabilities.

http://www.roberthancock.com/dell/xpsrproc.htm

very helpful once you’v read this you should be able to follow me.
First I got an Fc-Pga to Fc-Pga2 converter it looks almost just like this I grabbed it off ebay for cheap.

Then i got a 1.4ghz Celeron Sl6JU

http://www.cpu-world.com/sspec/SL/SL6JU.html

http://processorfinder.intel.com/details.aspx?sSpec=SL6JU

staying as close to the power regulations as possible it runs 1.5 volts and runs pretty well you also might like to know that this mother board also runs 512mb the dell document for this mother board doesn’t even mention 512 simply because 256mb ram sticks didn’t exist back then, I haven’t tried any higher amounts of ram.

here it is all sandwiched together

A Screen Shot of the My Computer properties

It's pretty stable actually and I've only had it crash once or twice and it runs pretty well paired with a more recent pci graphics card it could run pretty dang fast.