Converted internal hard drive into external, but cannot access via Windows!

Hello! I have an internal WD 750GB "green" SATA hard drive. I took the hard drive out of the computer and have put it into an external USB hard drive bay. However: when I plug the external hard drive bay into my laptop, windows recognizes the drive (including the correct model number) but says I need to format it before I can use it.

The drive is allocated a letter in "My computer", but if I try to enter the drive it asks whether I want to format.

The drive also appears in the Device Manager (but with no partition shown). I can click on a "populate" button and it then shows a partition with the correct volume size but this doesn't solve the problem.

I've also checked the disk by going Control Panel -> Administrative Tools -> Computer Management -> Disk Management and it shows the drive as being a "RAW" partition which is not correct.

I am running Windows XP but I also get similar problems when I check on a different laptop with Windows 7.

I've tried the external hard drive bay with 2 different drives and the same problem occurs so hopefully the drives themselves are OK (I can't check them in a different computer for now unfortunately). The drives appear to spin up OK.

I would prefer to avoid formatting the drive as it has data on it. I do have a copy of the data at home (in a different continent!) but would prefer to avoid waiting until I next go home.

Any idea what the problem could be? I wonder if the external drive bay can't recognize the partition and there is something I can do to fix this. Possibly the bay itself or both hard drives are broken (but why would Windows be able to see the correct drive model number)?