UxStyle

UxStyle is a bit of software that relaxes Windows theme signature requirements to enable third-party customization. Specifically, UxStyle consists of a tiny system service and a kernel driver that are loaded into memory where they hang out until reboot. No file system changes are made.

Operating System Support

Windows codenamed “Whistler” (escrow builds)
Windows XP
Windows Vista
Windows 7
Windows 8
Windows 8.1
Windows Server 2003
Windows Server 2008
Windows Server 2008 R2
Windows Server 2012
Windows Server 2012 R2
Windows codenamed “Threshold”