How do I tell if it's the HD that is bad or the enclosure?

[Kiva]

Hi all

I have a Seagate 160gb drive in a FW enclosure w/ an Oxford 911 chipset. The drive/enclsoure is starting to mount slowly and make weird squeaking noises followed by clicks. I just tried to plug it in and it wouldn't mount...just made a lot os squeaks and clicks. I then opened up Disk Utility and the drive then mounted.

How do I diagnose the problem? I've never had external HD prob's before..

thanks

kiva