Your question "which is not partitioned" i think, you have installed all on single partition by default installation profile, with separate swap partition.
please run some linux live from CD or USB and run gparted program. Next shrink main /dev/sda1 or /dev/hda1 partition, and if exist, move swap partition to the left. on free space create new partition and change its type to NTFS without creating any file system. Reboot your computer, and test linux is still working. Finally save your MBR record to any file dd if=/dev/sda of=/anywhere/MBR.backup bs=512 count=1 . It should be done because windows installer will overwrite it. If all is working, you can run DVD with windows7. After it start you should see 3 partitions, 2 unrecognized it is your linux partitions, and one at the end available for windows. select it partition and install as usual.
after this process computer will start only windows. do any available updates for it, and activate dual boot based on windows or linux, it is your choice.
Please read additional recipes about linux/windows dual boot. Without this cecture you will have a problem with selecting system you want boot.
Live is easier if both systems are placed on separate hard drives. You will boot any of that system by selecting boot device by bios boot menu.
Did you consider create additional system as virtual using VirtualPC/VmWarePlayer or similar virtualization software? Of course it is depended on your needs. For example, placing Windows inside virtualizator is bad idea if you are playing games, because you need direct access to graphics card for maximum performance, then windows should your main system. But in security view, better is linux as main system and windows as virtual. Wirtual in any way is nice, because you can use both systems at the same time.
Some resolution is VMVare Desktop, it has some facilities for increase 3D acceleration performance, but you must pay for it.