La dimensione massima di un file su FAT32 e' effettivamente 4GB, inoltre se formatti il fs con Win2k o WinXp la massima dimensione di una partizione FAT32 sara' di 32GB. In realta' con qualche trucco questo limite si puo' bypassare, il supporto MS dice:

You cannot format a volume larger than 32 gigabytes (GB) in size using the FAT32 file system during the Windows XP installation process. Windows XP can mount and support FAT32 volumes larger than 32 GB (subject to the other limits), but you cannot create a FAT32 volume larger than 32 GB by using the Format tool during Setup. If you need to format a volume that is larger than 32 GB, use the NTFS file system to format it. Another option is to start from a Microsoft Windows 98 or Microsoft Windows Millennium Edition (Me) Startup disk and use the Format tool included on the disk.

FAT32 supports drives up to 2 terabytes in size.