Adding a 2nd CPU to a HP workstation

Hi

are in need of more cpu power, have now a HP XW6400 with one 2.0Mhz dualcore xeon, need to add the 2nd cpu. Talked to the dealer, takes about 6 weeks for HP to deliver one, don't have that much time, deadline within a month, is it possible to mod a std xeon 2.0 dual core cpu to suit the HP dual cpu mobo? Dealer talked about voltage regulators that is a HP mobo special, whats that?
Anyone know if possible to bye a std off the shelf xeon cpu + "voltage regulator"(whatever that is) for this workstation??

Cheers,

k.