Yes you can, simply make a new partition on your HDD so you can use to install on it your Win 7 64bits version, make sure to have its respective drivers in hand (chipset, audio,video, LAN/Wireless) and to give it at the very least 40GB of space since the 64bit OS alone will eat around 20GB, from there you need to see how much extra space will be needed depending on which other programs you're going to install.