I would expect \device\harddisk\dr2 to refer to a disk device on channel 2 of the motherboard - which is typically a DVD or CD drive. So perhaps the scenario is you installed from a Win 7 install DVD, and when the reboot occurs, you had removed the DVD from the drive?
Otherwise did you do anything else in preparation for the install, like set the boot order to have the DVD at the top of the boot sequence? I am not familiar with a win 7 installation, nor is it clear what the state of your PC is before you start. For instance is this a completely new, empty HDD? Did you change the boot order at all?