1. Go to Start > Run > type REGSVR32 APPWIZ.CPL (capitals for clarity only, also note the space) and press Enter. Then run it again, Start > Run > type REGSVR32 MSHTML.DLL and press Enter.
2. If 1) is not successful, try this but create a system restore point first just in case anything goes wrong. Go to Start > Run, type regedit, press Enter and navigate to registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Management
In the left pane, right-click ARPCache and delete it. Reboot the computer. NOTE: The ARPCache key is where Add/Remove stores the details of programs that show in the list but it doesn't remove the details when you uninstall a program. After deletion, the key will be recreated by Windows.
3. If 2) is not successful or you can’t access regedit I suspect that you have caught something nasty.