Um, why the fat32 ?
Slower, less secure, less features than NTFS ..
Assuming you don't install anthing else except XP and maybe antivirus/firewall etc to the 10gig drive thats enough space .
Just install other programs to the larger drive or you will soon run out of space .
I think you may be able to convert the fat32 drive to NTFS without lossing anything, see click here