Yep, it'll work. The only thing you need to do is make sure that either...
1. The drive is formatted in Fat32 OR
2. The mac has ntfs3g drivers installed (to allow it to write to an NTFS formatted drive)
If your mac friend is simply reading from your hard drive, then an NTFS formated drive will also work. You only need the NTFS3G drivers if you want a mac to write to a NTFS drive.