Using the standard Windows 7 Disk Defragmenter, does the defragmenting process continue if I close the window after star a task manually?
There's no warning when I close the window, but I always wondered if it actually continues or not.
Yes, you can close the window and the defragmentation process will continue in the background, thanks to the Disk Defragmenter service (defragsvc).
If you want, you can use Resource Monitor to make sure it's still running. Go to the Disk tab and you should see svchost.exe (defragsvc) in the list. Select the checkbox in front of it and you'll see exactly which files it's currently defragmenting in the Disk Activity list.