In my experience, 95% of people have 10gb of files or less when you're just backing up their pictures, documents, movies, etc. Transfer time is about 30 minutes tops. Then you'll need 45 minutes to install Windows, 15 minutes to install drivers and set up the software, and another 30 minutes to transfer the files back to the computer after formatting. These are maximum times here. A decent machine can install Windows 7 in 20 minutes or less. Some machines require only a few drivers, meaning driver install time can be as low as 5 minutes. And the time it takes to transfer data depends on how much space the files take up and how many individual files there are. For example, 100 files taking up 20gb of space will transfer faster than 5,000 files taking up 5gb of space. I get a backup, format, and driver reinstall done in 1 hour quite frequently actually.