I have Ubuntu 12.04 as my main OS, but have been thinking of doing some dualbooting, would making a partition specifically for Windows and installing it to that partition mess with GRUB? or Would it be fine?
1st option : get a CD including Boot-Repair
The easiest way to use Boot-Repair is to burn one of the following CDs and boot on it.
Get boot-repair disk
2nd option : install Boot-Repair in Ubuntu
You can run this from terminal
Yes, it will mess it up, but...
If you install Windows 7 / Windows XP, installer will override MBR to point to windows boot menu -- which by the way don't allow you to boot linux.
If you boot some live distro from flashdisk/CD/DVD after succesfull windows install and update GRUB (and edit
Note that Windows 8 beta behaves little differently.
Windows would mess up GRUB, after you install Windows just use a live CD and follow these instructions.