po printout amount format for USD

hi ,

i am facing a problem . we have two imported vendors created on 2004 belongs to same vendor group.

order currency for both vendors is : USD.

when we give print out for PO,

for one vendor it is giving as :12,200.00 USD

for another vendor it is showing as :13.500,00 USD

i want to make both the vendors in same notation .

can any one suggest where diference in settings is .

rgds

Chalam