What does that mean exactly?

If it's recognized the right way, it should appear in My Computer and you can drag and drop any files to it, like you drag and drop files around on your c-drive.
If it isn't recognized, it won't appear in My Computer and you can't use it.

The things I wonder:
- Is the drive partioned and formatted?
- If it is formatted, is it formatted FAT32 or NTFS? Windows ME doesn't recognize NTFS, so it should be repartitioned and reformatted.
- Does this drive need a Windows ME driver?

I think your friend is the best person to answer those questions. He might not like if you repartition the drive and delete all his files doing that.

Hope this helps.