Windows 7 – Missing Free HDD Space

GParted should make it possible (I haven't used it), see comments.

The best way (that I have successfully used) is to use a utility to

1. Clone the Windows partition to an external drive (or just to the OS X partition if you have room (also keep in mind this is risky – it's good to have the full backup off the disk in question), using Winclone within OS X. It just creates an image file that you can move around to wherever you have space, until you do the restore.
2. Erase the Windows partition (it's ok, because you have the clone)
3. Create your new partition however large you want, using the Boot Camp utility within OS X
4. Restore the Windows cloned image to the new, larger partition
5. Use the utility to "expand to all free space"

Also, I would run a "disk check" on the Windows partition twice before creating the clone with winclone. Otherwise, restoring will most likely fail.

You can follow some of the steps from this question.

You have risks so you will want to make sure you know what you're doing. However, I do this all the time. I don't care about the "hidden restore" partition and I do not like having the entire drive as one partition. I'll download Ubuntu LiveCD www.ubuntu.com and use the preloaded GParted application to resize.

I've never seen an OS require Reactivation after partitioning. Adding/Removing Hardware, yes, but not partitioning.

The only thing that you may see is that the system will do a checkdisk but that is it. If you have any Bad Sectors on the drive, you may run into more complications. Always make sure your disk is health (CrystalDiskInfo) prior to doing something risky. Especially if you do not have anything important backed up.