External HDD woes! Please help!

I have had an external HDD that i put together for several months now, and it has always worked fine. the other night it started making bad noises and wasn't recognized by windows, or rather is recognized but doesn't "install" (shows up in device manger with an "!"). As i was trying to find if the error was with the drive (seagate Baracudda ST3200822A 200gb ata-100) or the enclosure (kingwin KH-350U-S) i found that the drive works fine when just hooked up to the ide channel on my motherboard, and the enclosure works just fine with another drive (old WD 120 gb ata-100). putting them back together the way i want it goes back the the same problem (wierd noises, not installed properly). I have no idea how to trouble shoot it beyond that, or what the problem may be. Help would be appreciated!

-Matt