|The Seagate GoFlex Replica works on Windows Vista & Windows XP so I'm puzzled why you say it does not work on your computer.|
However, if you want to delete the partitions and start afresh with a new, empty partition you can do it with the Disk Management console. (You've got to have at least one partition on a hard drive otherwise you can't write anything to it).
Control Panel > Admin Tools > Computer Management > Disk Management
In the bottom-right panel, find the ribbon that represents the GoFlex drive.
Right-click each partition and click "Delete Volume".
All the space should now read "Unallocated".
Right-click that and choose "Create new simple volume".
Then right-click that volume and choose "Format".
Upgrading to Windows 7 or 8
Be aware that you can't upgrade the OS on some older XPS models owing to lack of compatible drivers, so check the Dell website first!