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In most of the cases, that message appears when there's a problem with the filesystem, so you have to repair the disk. This doesn't mean that the hard drive is damaged.
First of all, open > About this Mac, and check Version. If it's 10.5 or 10.6, insert the Mac OS X DVD of the version you are using and press C key while your Mac is starting. If it's 10.7 or 10.8, press Command and R keys while your Mac is starting. After doing this:
1. Go to Utilities menu > Disk Utility (if you have 10.5 or 10.6) or open Disk Utility (10.7 and 10.8).
2. Choose Macintosh HD in the sidebar and repair the disk.
3. Restart, open Boot Camp Assistant and follow the steps to install Windows on the Mac