Dear Ahrkonh,
to use this custom themes from this site, first you need to do is download and install following application on your Windows 7 in this order:
1. Universal Theme Patcher (https://lalumasterit.blogspot.com/2012/04/aduuuuuh.html), if you have x64 OS, first patch 3 files from x64 setup, then after restart patch 2 files from x32 or if you have x32 then only patch 2 files from x32 setup and restart your pc,
2. Theme Resource Changer (https://dl.dropbox.com/s/rbz9y43z0jh...anger.rar?dl=1), install x64 or x32 depends what OS you have.
After this 2 installed application, copy-paste/extract theme files you get from this site to Windows/Resources/Themes/ directory on your PC and run it from right click Personalization window!