gparted is typically considered more powerful than fdisk for a variety of reasons, not the least of which is that gparted can resize partitions something that fdisk last I checked cannot do non-destructively. Partition Magic probably won't do it for the reason that s0be alluded to in your other thread, resizing partitions is not a guaranteed process, and particularly if the partition has been used for a long period of time, or it is close to full, it can be difficult to do due to fragmentation. I would FIRST AND FOREMOST make a backup as was suggested, then I would de-fragment your Windows drive, THEN I would use gparted to resize.
But understand resizing partitions does not always work cleanly, that is the most likely step to cause problems, and while I have never had it fail on me, that isn't to say it never will and having a backup before doing it is a must just in case. Resizing a partition means moving any data currently written to that area of the disk individually and relinking it in the FAT correctly, a lot of work pretty much for the program to do and a lot can go wrong, even though it rarely does in my experience. Again, in case it wasn't obvious I strongly advocate making a backup before doing anything