Start -> right-click "Computer" and select "Manage"
Click on "Device Manager" in the left pane
Open up the "Disk Drives" node in the right pane to find your flash drive.
Right-click on your Flash drive and select "Properties"
Click the "Policies" tab and select "Quick removal (default)"
Even with this setting applied, make sure that there's no activity on the drive before you disconnect it. Disconnecting the drive while it's being used can cause corruption and data loss.