How do I read RAW data from healthy drive via external encloser?

Problem reading data from healthy RAW drive.

Old Dell PC motherboard screwed up, so aim is to transfer data from my old dell HDDs on a new PC via an external encloser USB system. Purchased an Antec MX-1 encloser.

Have two SATA HDDs - both Seagate Barracuda 7200.7 160GB each, from an old Dell PC
These were set up as RAID0 and RAID1 on my Dell PC.

Trying now to transfer the data on these drives to a new PC via the Antec MX-1.

Correctly installed one of the drives into the MX-1, and connecting via USB to new PC. Vista installs the drivers and recognises the drive immediately. However when i try to access the new drive i get the message: "You must format the disk in drive D: before you can use it".

Obviously i dont want to format the drive because i want to save and backup the data on the drive first, but the MX-1 is not letting me access the data.

Looking in the Disk Management section on my computer the SATA drive im trying to read at the moment has the following properties:
Layout: Simple
Type: Basic
File System: RAW
Status: Healthy (Active, Primary Partition)

Why cant i access the data on the drive - what do i need to do to access it? Do i need both my two SATA drives to be connected at the same time? Or do I have to do something else to the drive first to be able to read my files again?

Please help,
thanks
Lewis