Windows 7 - Buffalo 1tb USB drive not recognized

I've got a relatively new 1tb Buffalo drive connected to a Laptop. Its been working fine, but now Windows 7 wants to format it.
On connecting the USB cable the disk spins up OK, but then the Win message comes up saying it wants to format the disk.
I'm far less keen on reformating the disk than Microsoft are . . because there's data on the disk that I want to keep.

Any thoughts would be most welcome

Check the hard drive with the manufacturer's diagnostic tools.
Hard Drive Diagnostics Tools and Utilities (Storage) - TACKtech Corp.
HD Diagnostic

thanks for the info.
Will one of the diagnostic programs work even if I can't access the drive ? - as soon as I plug the USB cable in Windows 7 comes up and says it wants to reformat the disk. The second problem is I've no idea what manufacturers disk Buffalo uses inside the DriveStation.

nice avata btw. Is that your arm ?

Dissconnect the usb drive next turn the laptop off, and even remove the battery if necessary - reboot and when windows is up and running connect the usb hard drive - dont forget to use the safely remove hardware icon in the task bar to disconnect the drive every time in the future. Hope this works otherwise those diagnostic tools theog suggested should be used - they usually have a utility to create a bootable disk if necessary, so dont worry.