I recall a OS-X theme for Vista... it installed using an exe file and went to Program Files. It was something along the lines of the old msstyles used by that StyleXP proggie, and to get rid of it was a pain in the butt, according to what I read. Although the theme could be uninstalled in Programs and Features in Control Panel, it left residual pieces and registry entries that caused GUI issues such as those described.
Apparently a system restore will not resolve the issue as important system files were changed, so you should probably do as DrJBHL suggests above....
Start Menu>cmd>right click 'run as Administrator'> sfc /scannow
This should restore your system to its original state... and please, if you wish to alter the appearance of your GUI in the future, use the Stardock suite of programs found in ObjectDesktop [found here... link] to achieve the desired result.... no system files are altered and they are safe to use. ObjectDesktop is the most economical way to purchase the programs; however, if you do not need the entire suite of programs they are available separately here or here, where other applications are also available.