Bad sectors just mean that the hard drive cant write to that particular area. When you run chkdsk it finds those bad sectors then basically locks them away so that the computer doesnt try to write to them again, thus keeping them from causing more problems. The good news is if it is only a few bad blocks your hard drive will be fine, the bad news is that depending on the age of your drive, these errors might just be the tip of the iceberg for a failing hard drive. You might look into getting a new drive and transferring your files over to it if there is anything that you cant easily replace.
Also, go to the website of the drive manufacturer and download the test utilities, if the drive is going bad, you might be able to get it replaced depending on the age.