Now, this is extremely unlikely, and doesn't correspond to my own experiences, but Microsoft says that in certain situations (crappy hardware, outrageous amounts of data, 32-bit install), the Windows 7 installation could take up to 21 hours to complete.
Chris Hernandez, a Microsoft Software Engineer, posted data on his blog tracking the time for both a 32-bit and 64-bit install for three different kinds of hardware and three different kinds of users. Most of the install times are totally reasonable (a clean install won't take more than 50 minutes, even on a really lousy machine), but one sticks out: The Super User.
The Super User has 650GB of data and 40 programs to be transferred, and apparently that in itself disqualifies it from testing with low-end hardware. But a 32-bit installation of this scenario on mid-end hardware has a listed time of 1220 minutes, or just over 20 hours. Even the best case scenario with the Super User (high-end hardware, 64-bit installation) is looking very slow, estimated at 8 hours.
My own installation took under an hour, even with 200GB of data to transfer, so these probably are conservative findings—that "high-end hardware" really isn't so high-end, with only 4GB of memory—but now we're curious. Has anybody's Windows 7 installation taken an inordinate amount of time? Let us know in the comments. [Ars Technica]