Power Quest Partition Magic has done everything I've ever wanted with altering partitions. This includes increasing the size of a Boot Partition at the cost of space from a 2nd partition on the same drive.
I'm happily using V7 with Win/XP.
The current version is V8 and is Free to try, $69.95 to buy, from
Download Partition Magic 8.0
What isn't clear is just how much you can achieve during a free trial.