If you're currently a Windows Vista user, there's a good chance you'll be switching over to Windows 7 this October. Microsoft's latest edition to their OS line-up is essentially a combination replacement and apology for the dire mess that was and is Vista. Thankfully, those dark days are soon to be behind us, and with Win 7 at our backs we'll be free to venture forth into a bold, somewhat-less infuriating future.
However, before you start that upgrade there are a few things you should know. Arstechnica (via Gizmodo) reports that Microsoft set a team of engineers on the task of figuring out how long Win 7 takes to load on various machines. Most of the numbers they got were pretty good; a clean install on a low-end machine should take around 40-50 minutes (depending on whether you install the 32 or 64 bit version), while a clean install on a high-end machine only takes 30-35 minutes.
There were some outliers, though. Microsoft found that a 'super-user' with 650 GB of data and 40+ applications could take more than 20 hours to finish installing. Even with a high-end device, the whole process still took around 10 hours.
The message here is clear; if you're going to reformat and switch to a new OS, clean your computer up first. Back everything up on a separate drive, wipe it clean, and start fresh. It will make sure no issues linger on in your box from OS to OS, and it'll save you a whole bundle of time.