If it's a USB drive, try unplugging it while the computer is turned off...
Turn the computer back on and then plug the cable back in to see if Windows recognizes it.
If it doesn't, see if the Device manager shows any errors...you may have to reinstall the driver for it if Device Manager is showing any type of error...you may also need to go to Maxtor's site to see if they have a Diagnostic Utility you can use in Windows or DOS to see if you can test the inegrity of the drive...
Here's a link to their
DiscWizard software program.