I have purchased an officially Microsoft re-furbished Dell OptiPlex running a Pentium D 3.40GHz 3.39GHz. I believe it dates from 2007 and was originally spec'd with Windows XP. It has been supplied with an authorised Windows 7 OS 64bit, which runs very well, but with one big problem - the Microsoft Games (card games - Solitaire etc.) will not play - they just throw up an error screen "...cannot load the executable...) and then shut down. Is this a hardware problem that cannot be resolved? Or is there a fix?
Looking at this thread this is likely a OptiPlex GX520 or GX620, use these drivers:
http://dellwindowsreinstallationguide.com/driver-sets/optiplex-desktops/
Ensure that Windows 7 is clean installed.