If the options are Install and Upgrade, I think you have gone too far.  Instead of clicking Install Now, click on the link at the bottom "Repair Your Computer".  If it truly is not there, then use nat's links in his signature to download a full copy of the Windows 7 media for the repair.
Click StartType: CMD, right click CMDClick “Run as Administrator”At the Command Prompt, type: sfc /scannow
Windows 7 - corrupted file / missing msvcp80.dll