Just wanted to update this thread as so many people should relive Doom and Doom2 with this mod.
Really really simple installation, if you want to keep it as vanilla as the original games then get zDoom and the Brutal Doom mod. Copy the zdoom files to your doom or doom 2 install directory, copy the brutal doom pk3 file to the same place, drag the pk3 file onto the zdoom.exe file, zdoom will launch and away you go! The bitmap graphics are still there in all their blocky glory but with the added mayhem of the brutal mod, it is so much fun.
Get it.
PS, yes zDoom and the Brtual Mod work with the Steam versions of original Doom's incase you dont have the orginal disc/CD.