Hello, and welcome to the Windows 7 Forums.
You should still be able to perform an "Upgrade" using an OEM copy, though there are several different variations, so it may be different for you.
Performing an "Upgrade" is not a recommended route anyway.
You should always backup your programs and data, do a "Custom/Clean" install of Windows and re-install your programs etc.
The reason for that is, by upgrading, you're keeping everything and only re-installing Windows. This leaves conflicting programs, incompatible drivers, as a result, your PC will usually "crawl" along slower then it did before the upgrade, and in many cases, be so instable that it will crash constantly.