Missing space

Hello,
I recently bought a Maxtor 600GB external HD. It was ntsf, but i needed a more universal format, so i converted the drive(partitioned the whole drive) to FAT32. But when i did this 'my computer' shows 251GB out of 596 of available free space and there are absolutely no files on the drive. So what happened to 300GB+ of space? Is there anyway of getting it back without converting back to ntsf. I would like to keep the external drive in FAT32 format so my ps3 can read it. The program I used to format the drive was "HP USB Storage Format Tool". Swissknife does not work as it only partitions 94GB into FAT32, leaving the other 500GB in ntsf. My OS is windows xp.

Any help will be aprecciated,
Mike