Do not attempt to use GParted to Shrink a Windows 7 Partition.
A bug in the GParted Live CD impacted how it updated the Windows boot sector if the start of the Windows partition is moved. This is one culprit but not the exclusive problem with resizing an active Windows 7 partition. In this case GParted may move the start point of the Windows boot sector at sector number 2048 instead of moving it to sector number 63.
Another source indicates that Windows 7 is designed to purposely store important boot data at the tail end of the partition. Even a very small change in the size of the partition by moving the end of the partition inward can destroy this boot data. Some recommend that you defrag your windows drive before shrinking. Even doing so the chances of a problem are significant.