I want to bring some movies i have on my i-mac to America with me. I brought a 500 gig external hard-drive that is formatted for windows. i need to reformat it so it will recognize my mac so I can copy them and windows so I can use them on an ibm machine. there are several choices, which format options do I use?

thanks

You could format it using FAT32 but that has file size limitations. You say it is already formatted for Windows but with which format? If it is NTFS your Mac should be able to read the disc but not write to it. A free driver download will allow your Mac to write to a NTFS drive as well so both the Mac and Windows machines can use the same drive.

http://www.apple.com/downloads/macosx/system_disk_utilities/ntfs3g.html

make smaller partitions less than 32GB...

but there is also a problem with files bigger than 4GB (most HQ Movies are bigger)

best is to format ext2 and install ext support on the windows machine.