Here's one idea: Open the command prompt by searching for cmd in the search bar. Click on cmd and type this command: C:\user> format H: /FS:FAT32 Press enter. If it asks for yes/no press y. Press enter and your USB drive should be changed to the FAT32 format.
The Windows GUI limits you from formatting a drive if it is over 32 GB with the FAT32 file system. It is just an articifial limitation, and it will still mount such a drive formatted that way/.
Sorry, on second thought I'm not sure if the command prompt will let you do it either. You can easily download a program called fat32format.exe from Ridgecrop Consultants here: http://www.ridgecrop.demon.co.uk/index.htm?fat32format.htm