Metaphorically - 6:31 pm on Sep 11, 2006 (gmt 0)

Microsoft has been producing guidelines for PC manufacturers for at least 8 years. The oldest one I remember was called PC98 (there might've been a PC95 but I don't remember). That's when we got the different coloured boxes around the ports on the back with the little icons next to them.

At some point it became part of their logo program. If you wanted to put the "Designed for Windows 98" logo on the computer then it had to conform to those guidelines.