What, excuse me, the fuck? I never knew one could do this. Thanks!
Back when Windows 2000 was the new thing, I used to put "Program Files" on another disk with this. Starting programs became faster too, as things loaded both from the OS drive and the drive where the programs were installed.
It's even available in the regular UI, open "computer management" go to the disk section and many of the 'magic' things about drives in windows world are just UI toggles