Problems w/ Uninstalling 8 and Reinstalling 7

I installed WB 8, but after a month or so, I decided to go back to WB 7.  I first uninstalled WB 8, then from the SD Central tool, I re-downloaded 7 and installed.  Each time I attempted to launch it though it says my subscription code is outdated or invalid.  I tried several times, copying/pasting the exact code directly from my subscription page and from the email confirmation but neither worked.  My subscription is good through Jan. 14, 2014.  I finally did a system restore so now I'm back to WB 8, but I still would like to go back to 7.  Does anyone know how to do this?  I'm on Windows 7 64-bit still.