My Passport Essential switch to Windows 7

My unit works perfectly with Windows XP.  When I plug it in via USB to my notebook (Windows 7), the notevook does not recognize its existence.  Please advise.

Welcome to the Community.

There are times when you may have to format an external hard drive when jumping straight to Windows 7 from Windows XP. Try to confirm if your hard drive is displayed on Disk Management. If it is, you will need to format/erase your hard drive in Windows 7 before it can be used.