Windows 7 is just around the corner and for those upgrading you might possibly need to set a day aside for the upgrade to install. Microsoft have run some testing as they wanted to make sure that a Vista to Windows 7 upgrade was quicker than a Vista SP1 to Vista SP1 upgrade. You might think that is a typo, but an SP1 to SP1 update simply re runs the service pack update and runs through each of the routines. Also, a test from XP to Vista is not the same as a test from Vista to Windows 7 which is why SP1 to SP1 was chosen.
The results they found were varied from taking just 30 minutes on a high spec machine that simply had Vista installed with no extra files or applications installed all the way to a mid range PC taking 1220 minutes for the 32 bit install with converting 650GB of files and running 40 applications. See table above for results…
If you are planning an upgrade then the above screenshot shows what you could be in for. What I recommend is a clean install of Windows 7 and just backup your files to an external or secondary drive if possible or back them up over a home network. This will ensure the cleanest possible install. Via: Ars