The 90 second ad, created by Miami's Crispin, Porter + Bogusky, is designed to counter Apple's "I'm a Mac, I'm a PC" campaign, which features a geeky PC guy unable to keep up with the "hip Mac user".
The ads were remade for the UK with comedy duo David Mitchell and Robert Webb.
The Microsoft spot shows Seinfeld trying on shoes with Gates in a discount shoe shop and doesn't mention any specific Microsoft products, such as the much criticised Windows Vista operating system.
The immediate reaction to the ad on the web has been fairly negative. A blogger on ZD Net posted: "I don't get it. And seeing how the punchline was, ummm, Bill Gates adjusting his shorts, I don't think I want to get it."
Some YouTube users were left equally baffled by the ad. A user called AnimeZombie91 said: "I don't think I'm fully getting this ..." while x7c went simply with "WTF ?!".
The blog Crunch Gear said: "While the ad doesn't really tell us anything about Microsoft or its products, it does tell us that someday computers will be edible. So there's that. Gates is kinda funny too."