I was fixing some problems

Question

I was fixing some problems my friend was having with her Compaq Presario V600 (o/s Vista Business) and went to re-start once I was done and it will no longer boot. It comes up with the screen where you can choose to boot in safe mode and when you choose it it freezes when it is looking through the system32 files.Have tried booting from a normal Vista CD and it does not have the C: driver, so I asked her for the disc that came with the laptop and she said it didn't come with one. When she asked at Harvey Norman where she bought it they said you don't need a disc, its in the computer.... does this make sense? How do I do this?