External HD in FAT32

I bought an internal 400gb hard drive that I put in an enclosure to use as an external hard drive. Upon installing I split the HD into two partitions 100 and 300gb with the supplied software.

However, I have a mac now and would like to be able to read/write to the HD between windows and os x on this HD. And apparently FAT32 is what I should have put the partitions into.

My question is what should I use to change the partition/s into FAT32? The supplied software wont do this.

*edit*

Oops, e xternal HD

 

I have a Western Digital 120 Gb external that is FAT32. FAT is not defined for more than about 32 Gb, so I had to get the FAT32 formatter from WD. Perhaps Partition Magic or some such can handle it.

 

You can't convert it back without Partition Magic.

Are the partitions really full though? I'd connect it to a Win PC, copy the data from one partition to the other(maybe the 100GB to the 300GB). Delete and re-create the partition as FAT32. Copy the data back. Then, depending on how much data was originally on the 300GB partition, move it to whatever's left on the 100GB, and the balance onto that local machine, if you've got enough room to temporarily pull it off. Delete, recreate that partition as FAT32. Copy data back over.

I wouldn't bother buying or pirating Partition Magic just to do this.

 

And don't forget the <4gig size limits with fat32 depending on if you have any large movie ISO files.

 

Thanks for the advice everyone.

What exactly does the 4gb size limit with FAT32 mean?

 

The FAT32 file system can't support individual files larger than 4GB (because it's 32-bit - similar to how 32-bit processors and OS's can't handle more than 4GB of RAM).

I've noticed than in addition to DVD .iso files, this is a problem with some new games (Condemned springs to mind) that keep most of the game data in one large compressed archive that exceeds 4GB.