You probably can... although, any data on the drive will be deleted.
On the desktop, right-click on My Computer and select Manage.
From there click on Storage --> Disk Management
Now you should see the 4 mb partition of your usb thumbdrive. Right click that small partition and delete it. Now all of the storage should be unallocated. Right click the unallocated space and select format. Format it to FAT or NTFS and you're good to go. You may also have to reassign a drive letter as well, but it should not be too hard to do that. Right click again and select cheange drive letters and path.