Try
googlingfor a driver. You'd be best off if you knew who the manufacturer is, but it's possible that a different manufacturer's drivers may work fine for the drive.
It would also be good to check out the device manager (right click on my computer and select properties) and see if it is listed there as "unknown hardware"...if it is then you need to remove it from there before you'll be able to install a driver.
If it works in dos, you always have the option of copying the files there. The only downside is that you'll lose long filenames, which, depending on what you're backing up, may or may not be important.