Howtogeek shows you how to get the classic-style themes back on Windows 8
Windows 8 no longer includes the Windows Classic theme, which hasn’t been the default theme since Windows 2000. If you don’t like Windows 8’s bright colors, you can get classic-style themes for your Windows 8 desktop – or create your own.How to Get Classic-Style Themes Back on Windows 8
These themes aren’t the Windows Classic theme that you know and love. They’re Windows 8’s High-Contrast theme with a different color scheme. Microsoft has removed the old theme engine that allowed for the Classic theme, so this is the best we can do.
Note that using a Classic-style theme on Windows 8 won’t improve your desktop performance, despite what some websites may say.