GParted should be able to resize ntfs (see the features
page). If it failed, make sure that you didn't have the partition mounted you tried to work on and that you only try to do one action at a time. I think it's possible to "queue" several actions and then do them all in one go, but that might not work out after all..so if you tried to, for example, shrink one partition and enlarge another etc., try again by first resizing one partition, applying that, then doing the next step etc. That worked for me at least (removed ext3 partitions from a harddisk(, applied changes), then made a ntfs partition fill the empty space).
Also when shrinking an ntfs partition you might want to run a defragmentation tool on the partition first, for example the one that comes with Windows. And if GParted doesn't seem to work the way you want, you can always use Windows-native software (like Partition Magic).