Alright. That answers a couple of things for me.
Your system is not set to boot from the Optical Drive. Cause it should not reach that point with the Vista DVD inserted. That should kick on right after the Dell logo leaves the screen. So you will have to go into your BIOS and set your boot priority to Optical first then hard drive.
The reason you are getting this is because of the failed repair. It is trying to boot Windows. But since the boot failed, you dont have a OS that works. Just like i first said.
Your install right now is corrupted. Which is why i said you need to go back and redo the repair to get a functioning OS. Right now it is corrupted and wont boot no matter what.
So your options are to do a repair install again, or to set the boot priority correctly so that you can use the Vista DVD.