Yes, you can.
Go to Windows Anytime Upgrade (Click start and type it in).
Click on Go Online.
Once the page is loaded, select Windows 7 Ultimate.
Next you need to fill out the billing, the paying, and a few other steps before your able to get the upgrade.
Install the upgrade, then one you boot into Windows 7 Ultimate, follow the steps on this website: http://windows7center.com/tutorials/how-to-download-and-install-windows-7-beta-language-packs-mui-packs/