Look at the other thread you posted your issue in-it's got good stuff. Basically, if you choose to not back up, you're on your own, but you probably won't have any problems. Using an external drive to back up to is a Good Idea™ for a number of reasons, and you can get useful, affordable enclosures you just put any drive you want into for "not much money" (I have one I got for about $30 that I put a $99 300GB drive into-it works great!). And again, backing up is a Good Thing® anyway.
You should start by using the Boot Camp Utility (in the Utilities folder of your Applications folder) to "restore the start up disk to a single partition". Once that's done, boot from your OS X install DVD and use Disk Utility to repair the disk appropriately. This process may take a while, but it will make your disk much more reliable because it will fix just about everything.
If the error message told you to reformat, things are even simpler. Back up JUST YOUR DATA AND PROGRAMS, then boot from the install DVD and start fresh. Once you're done with the new installation, restore your data and programs and you're back to a fresh start with a clean drive.