Welcome to "Dirty Bit"
What you're experiencing is what Windows 7 refers to as "setting the dirty bit" and what you have to do is unset that bit. Every time Windows 7starts, autochk.exe is called by the kernel to scan all volumes to check if the volume dirty bit is set. If the dirty bit is set, autochk performs an immediate chkdsk /f on that volume. Chkdsk /f verifies file system integrity and attempts to fix any problems with the volume. It is usually caused by a hard shut down or a power loss during a read-right operation on that particular drive.
That's easy to fix. First click <Start> <Run> bring up a command prompt by typing in "CMD" and type " fsutil dirty query d: ". This queries the drive, and more than likely it will...