Someone had a guide on how to install the Vista experience without the Vista baggage attached. Use the search button to find it? Otherwise, Google showed a number of options for Vista themes.
Unless you need help installing them? Specific, please. <3
If the file you downloaded is in .msstyle format, than you need to perform the uxtheme.dll patch. Google it and you should get a link from softpedia, which you should then run the file it gives you.
If it is in any other format, you would need a program called "Windowblinds".
I wouldn't recommend doing it though, or installing any themes for that matter. All it does is slow down your computer because it has to repaint everything constantly.