Rom-Freaks isn't bad:
http://www.rom-freaks.net
I checked, and it's got Doom 64 (
http://www.rom-freaks.net/download-9...e-Doom_64.html), though if I were you, I'd just play the original doom; I recommend zdoom. Emulator controls are often a bit weird, as they also have to emulate gamepad controls, which can cause problems, unless you have a gamepad for your PC. Platformers are a pain in the ass for example.