Windows 7 does not recognize file system of external hard drives connected through ATA

Windows 7 does not recognize file system of external hard drives connected through ATA

I have a couple external ATA drives (Maxtor 320G) in HD enclosures(USB) that I want to use as internal hardrives. I assumed that it would be as easy as removing them from their enclosures and installing them in my windows 7 (x64) pc. However, while the drives can be seen from windows, the contained data cannot.