Just like reborg said, GParted -- LiveCD is one such tool.

However a point to note, when you install Windows after Linux, you wont be able to boot Linux as windows boot loader will rewrite the grub settings for MBR. (its m$ afterall)

You might wanna run a grub-install /dev/hda (or whatever is your primary drive) to fix the issue and get a dual boot screen during boot up

~s4g3