1. Consider carefully your reason for wanting to do this...
- If you are expecting to be able to plug the NTFS drive into your PS3 and play large games/videos there is no point, the PS3 doesnt support the NTFS filesystem and you won't be able to acces any of your files. (*unless some dev has written a nice NTFS filesytem driver i've not seen yet!)
- If you simply need a drive for your PC to store large files on, then you shouldn't have any worries doing this.
2. If (having considered the above) you still want to proceed, there is a free, built in (command line) utility in windows XP and above that allows you to convert from FAT (16 or 32) to NTFS.... it is called "convert" (see http://support.microsoft.com/kb/307881
for full details). Microsoft confirm on this page that it will retain all files, although as with any hard disk operation there is a small risk of corruption (you should always backup!)
Note: Converting from Fat32 to NTFS is a one way process. There *might* be third party tools to revert (unlikely), but i suspect you would actually need another drive to copy to, then reformat as fat32 and finally copy back!
Hope this helps.
p.s. To reformat to a Fat32 partition that is larger than 32gb, you won't be able to use the built in windows format tool. There are tools out there (i think western digital release one) to do allow you to do this.
The default format tool in Windows will only allow you to format to 32gb as Fat32, unless you format to ExFat which allow much larger partitions (but does not work with PS3)