If it was installed on the windows partition and the windows installation is there, then it didn't format the partition, which means it would have to be in whatever filesystem was there before, and Windows only runs off FAT or NTFS, which version of windows is it? If it's 9x, then it has to be fat (fat32 for 98 but not 95). If it's 2000 and up, it's probably NTFS unless you specified specifically for it to be fat32 (dont know why one would want that).