I have a drive with ubuntu 12.04 currently on it.
Can I and if I can then how, install Windows 7 on that same drive without removing the ubuntu installation? (being able to use both)
Please notice that I already have ubuntu 12.04.
First you need a partition to install to. If your hdd has enough space, use GParted to shrink your existing partitions and create a new NTFS one. Do this while running from a livecd/usb It's a really bad idea to modify mounted partitions.Also, it is always a good idea to backup your data first.
Now that you have a suitable partition, go ahead and install win7 as you would otherwise and select the said partition as destination. The windows installer will mess up your MBR and boot loader so after completion of the installation process you need to repair grub. There are some fine tutorials in this site. Just search for "repair grub"