DON'T TRY THIS IF YOU WANT TO GO ON THE SAFE SIDE!
I do not believe that fdisk will resize any windows partition.
however many distros now have a utility that will resize a fat32, or NTFS partition. however they can cause damage to the partition (I have never encountered any problems, but I do not use windows enough to care if it breaks on me). you can also get these programs seperatly from an install
that one should work fine.
if you really want to go on the safe side I would go buy another harddrive and install linux on that.