They actually will run from different installs. I have reloaded in my D drive, and GameGuru in my C drive. They co exist with each other as GameGuru is installed in the Steam Folder, Where Reloaded is installed in The Game Crators folder.
Even if both were installed to C drive.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit