Guest Post by Justin. Justin is a small business owner and computer technician with Protocol16, supporting small and mid-sized businesses as well as consumers in the metro area of Portland, Oregon.
Microsoft has stated that some in-place upgrades from Winodws Vista to Windows 7 could take as much as 20 hours, or more, to complete.
Upgrade times are dependant on machine calibur and the amount of drive space the user is taking up. The worst times were achived by mixing a medium calibur machine and a larger profile of 650GB of data and 40 applications. This test took so long that Microsoft decided not to test a low calibur machine mixed with a very large amount of data.
Typical times for medium calibur machines and general users were around 2-3 hours.
Source: Computer World