Windows Vista only: By default, Windows Vista doesn't allow you to install custom colour and window decoration themes, unless they've been specifically reviewed by Microsoft. With a set of Uxtheme Patches, and a willingness to roll up your sleeves and patch your system, you can enable custom themes and tweak your colours, windows, and other desktop parts to your heart's content. The How-To Geek has a step-by-step guide to installing, patching, and enabling custom themes, and it's highly recommend that anyone trying it out back up their files and create a restore point before pressing on. Having said that, there are some pretty slick themes out there, at deviantART and elsewhere. Uxtheme Patches are free downloads for Windows Vista (standard and SP1) only. Image from NEXTLevel theme by patrickgs.