Modding Windows is akin to building a sand castle. It might be fun, beautiful, but very much impermanent. You can expect it to be washed off with the next Windows update.

I've done it before on Windows 7. Resized system clock, resized start menu button, removed "Terminate batch job (Y/N)?" warning in cmd, etc.

Most annoying is that VirtualBox stops working with the patched uxtheme.dll.

...

Life on Linux is great. My modifications stick for as long as I want. Permanently if I get my patches upstream.