resize bootcamp partition

Hello,

I have a bit of a problem. I am running 10.5.2 on my MacBook, and I
have a windows vista partition that is configured for boot camp and
Parallels. My problem is that when I originally created my partition,
I was somewhat short-sighted, and now the partition is nearly full. I
purchased the "upgraded" version of Parallels that includes an
Arcronis utility that is supposed to be able to increase the partition
size. But this operation has failed every time I have attempted it
(about 5 times with attempts at 5 different sizes). I am wondering if
anyone here has had a similar problem and how and if they were able to
fix it. While the problem is not yet critical, I only have about 4
gigs of free space left on my windows partition. I would sure like to
find a solution for this.

SL