Ok, here's this weird request, shame on me, I know
So, I want to install Windows 7 on my laptop, alongside the Ubuntu 12.04 that is running there right now. For gaming, obviously, cause not all games run via Wine or in VMs.

Since I don't want to screw up my Ubuntu installation (with my documents and all), I'd better do this carefully, if at all. So I need some good advice. Most of the tutorials suggest installing the Windows first, and then proceed with installing Linux, since the Windows installer is jealous and doesn't treat the GRUB politely. In my case, that is not an option - the Ubuntu is taking all the HDD, and the best I can do is shrinking the main partition, allocating new one and installing the Windows there.

So I am looking for advice how to do that properly - do I need to back up GRUB config before installing Windows, how to install Windows without destroying Ubuntu install, and how to fix the bootloader after the Win is installed. Or maybe you'd suggest to abandon the whole idea as totally crazy, I can take that as well.