Windows ME usually recognises most external devices.
Is it a USB drive, and when you plug it in, are you getting a warning stating that certain files can't be found?. (these are usually USBNTMAP.SYS and USBSTOR.INF ).
If this is the case, this was a common problem with Win ME, and if this is what you are experiencing, let me know, and I will post a couple of links on how to try to fix this.