I have never seen a modern USB hard drive that required a driver in Windows XP. They are a plug and play device if connected to a working USB port. I own one and it has never needed a driver in Windows XP.
Seagate doesn't list a "free agent go 320gb" but they list a FreeAgent GoFlex, FreeAgent, and FreeAgent Classic
It may have some installation software available but it's not needed in order to make the drive work.