DEWilbanks, Thank you for using the Dell Community Forum. The support center looks at the service tag and sees what OS the system was shipped with and then provides updates to that system. You would need to manually search for updates for your system. I see no way to add the new OS that you installed.
I have a Dimension 9200 that came with Windows XP.   I just installed a new drive and installed Win7.   I downloaded Dell Support Center and installed it and wanted to use it to get all the latest updates, etc.   It only offers me the Win XP updates, not based on Win7.   Is there any way to change my configuration so that DSC "knows' that I am now using Win7 and not WinXP?    
Dell Support Center - how to change operating system