reason is because w8 uses a hiberfile between shutdowns and that seems to interefere with software installations at times.
Not sure where to post this but: I have been helping a friend adjust to Windows 8.1. I put in the Shell extension to start up so it looks more familiar to her than the Windows 8. Every time Windows does an auto-update, Shell gets moved to a "removed app" folder on her desktop, as does her Quicken. Why? How can we change that behavior?

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