You can do it on other consoles, too, though they require a mod chip.

I recall reading an article on how to hack a NES cart and how to play around with some of the data, but I know it didn't say anything about actual cart flashing and loading new games into them. You may be SOL on this one, though if you wanted to get the same experience (sort-of), you could get a NES->USB converter, and with a video card with TV out and an audio cable that switches the digital jack (what your PC uses) to stereo component (what your TV uses), you could at least play using the NES controller on a TV.