GoodiPhone reports that a group of developers have managed to install and run Windows 95 on the iPhone. With the help of a Bochs emulator and an original Windows 95 image, they managed to get the Microsoft OS running on Apple's iPhone. Unfortunately, it seems performance was an issue so they're eager to try the same test on an iPhone 3GS.
The developers also tried to get Windows XP running. Check out the video and screenshots below.
And for old time's sake, here's the Weezer video for "Buddy Holly", which came bundled with Windows 95.