Hi,
Unfortunately your dump file was corrupt or at least the debugger was unable to read it. Do you have the pagefile turned off or set to a figure below 200MB? If so this will stop dump file creation.
Did you install windows 7 as clean install, meaning did you boot from the windows 7 install disk?
Try this, find command prompt in the start menu, right click on it, hit properties and then run as admin. Type:
sfc /scannow
Press enter and await results.