External Drive question for use on a Mac and Window machine

[Random Betrayals]

I am in need of a backup/portable hard drive for use with my personal Vista computer at home and with the Mac computer at school. Is it possible to have one drive for use on both, I have gotten conflicting answers to this point so far so I wanted to check with the masses. I have seen the technical specs of several drives state that they are compatible with windows xxx or mac os xx but none have said anything about simultaneous use.

Any help is always appreciated

[valve1138]

If it's formatted FAT32 a Mac can read and write to it just fine.

I think you need third party software for OS X to read AND write to an NTFS formatted drive.

[markintosh13]

If you format the external HD as FAT32, then it will (with some limitations, like a 4GB file size maximum).