Windows 7, released October 22 2009, is the latest and greatest operating system offering from Microsoft. The official system requirements indicate that you need a 1Ghz processor, 1GB of RAM, and 16GB of available disk space. A member of The Windows Club Forum defied those requirements, and managed to get Windows 7 running on a Pentium II 266Mhz.
The PII 266Mhz was released by Intel in 1997, so we're talking about 13 year old hardware. The forum member's machine had a 4MB graphics card, and Windows 7 "ran" on both 128MB and 96MB of RAM, but complained of too litle memory when the machine was configured with 64MB.
His next attempt will be trying to get Windows 7 running on a Pentium I 166Mhz with a 1MB video card. Useful? Of course not. Does it prove something? Not really. Still, it's cool.