|If you do go the re-install path - and presumably it will be with a recovery disk... Fisrt take steps to safeguard your data.|
Bet a Knoppix or Ubuntu disk and boot with that. Then you can access and copy data to optical-media... Would be wise to do this regardless of how you start to resolve the problem posted...
Knoppix can be downloaded as an iso file at burned to a disk; similarly Ubuntu.
Both are freebies..