If you upgraded within the last month you will still have a folder in the root of c: named windows.old and that contains everything Windows 7 needed to fly, included your personal files. If you can find the .exe for the game, copy it into the same folder in c:\windows then do the same for the file cards.dll in c:\windows.old\\windows\system32, copying it to c:\windows\system32.
If it isn't in System32, try ProgramFiles\Microsoft Games\Freecell or in a 64 bit system, Program Files X86|Microsoft Games\Freecell