If the motherboard does not support it, the processor just won't fit in. If it's a socket 939, any socket 939 proccessor should fit. Maybe if you give me a link to what your looking to buy, I'll have a look and let you know.
Hmm... Ok, should work as long as it's compatible with your motherboard, if it's on ebay then maybe send a question to the seller asking if it will be.