From what I read above, you had no problem in shrinking windows, an operation that can cause problem more often than Linux. I hope that you did already check that your windows system boots and works as expected, before going further.
The eventual problem has to do with the modification of the partition start sector, something usual with the windows OSs. That could happen with cylinder-aligned system hard drives in case you tried to make any partitioning operation with the MiB alignment option activated. Then, there was an implicit MOVE operation that could cause the start sector changing position. After that window wouldn't start and you had to restore the boot function from the installation dvd. Anyway, since 10-15 years the MiB alignment is the default for almost every system. Linux has been not sensitive in that problem, so I don't think you risk from this. Even in case of problem you can easily "repair" the boot loader.
HOWEVER, the suggestion of taking and keeping backup copies from time to time and especially before such important partitioning operations is always valid, from myself and from the entire GParted team. There are many causes for data loss, related to hardware failure events, power problems etc that aren't known before. Intense hard drive operations can be fatal for a hard drive with some hardware problem. Unknown bugs can be another source of problems. From my experience. a big part of the forum threads concern loss problems that could be avoided with a backup taken in time.
Another point on the warning: moving the start of a partition makes the entire partition content to move block by block. This operation can be long and stressing for the hardware, and this makes the hardware-related risks more relevant. In case of laptop computer make it work on the sector and not just on battery. For a desktop computer, try to use a UPS unit. And a good backup makes everything safer: 99% of the times it is not needed. nevertheless the bad 1% makes it valuable.
A good practice is to keep an emergency boot medium on cd/dvd or usb device. Windows allows you to make such a device. Linux live media are useful too as well as tools like "System rescue cd".
*** It is highly recommended to backup any important files before doing resize/move operations. ***