They are two different socket types. One is a PPGA478 and the other is a PGA478. You can get the info here:
T9300:
http://ark.intel.com/products/33917/...Hz-800-MHz-FSB)
T5250:
http://ark.intel.com/products/30786/...Hz-667-MHz-FSB)
Sorry but one will not work in the other socket. It will fit and boot, but you will not be able to configure the chip correctly.
If you can return the chip, then I would suggest that. If however you cannot return the T9300 chip you might try and sell it to recoup at least some of your investment.