Then you can only store files on that drive that are less than 4GB in size... there is no way around this.
If you want to put a VM image on the drive that is larger than 4GB, you will need to reformat the drive to a format that supports files larger than 4GB.
NTFS can support files larger than 4GB, but is read-only (without modifying preferences or installing 3rd-party software) under Mac OS X. HFS+ can support files larger than 4GB, but is a format that is only readable under Mac OS X. In order for Windows to read/write HFS+-formatted drives, 3rd-party software would need to be installed on the Windows machine.