Fastest time for move from Vista to new OS is 1 hour and 24 minutes; clean installs are faster

Microsoft said Friday that some "in-place" upgrades from Windows Vista to the new Windows 7 may take some users over 20 hours to complete.

The best that users can hope for is a 1 hour and 24 minute process, said Chris Hernandez, who works in the Windows deployment team, in a company blog published Friday.

So-called "clean" installs, where the user overwrites an existing edition of Windows to end up with the OS, but no former data or applications, take less time: from 27 to 46 minutes.

Hernandez said the in-place upgrade times were obtained from lab machines in three different configurations -- labeled low, mid-range and high-end -- with three simulated users: a medium user, a heavy user and a super user. The profiles differed in the amount of data and the number of applications that were on the PC before the upgrade to Windows 7.

The medium user profile, for example, assumed 70GB of data and 20 applications; the super user profile, on the other hand, contained 650GB of data and 40 applications.