Norton Disk Doctor finds problems on C drive

I have a Dell computer.  It’s about 4 years old.  Right from the
beginning Event Viewer showed that there were bad blocks on my hard
drive.  Dell said I should swap out the disk before it crashed.  They
said I would have to reinstall everything from scratch.

I’m handicapped and the thought of doing that was just too much for
me.  Instead I bought an external drive and run Norton Ghost backups
periodically.

Four years later and nothing has happened.

Today I bought Norton Internet Security 2009 and Norton System Works.
System Works comes with Disk Doctor.  When I ran it, it found the bad
spots on the disk.  It asked me if  I wanted them to be fixed.  I said
no.

What should I do?  Should I leave well enough alone?  Exactly what
will Disk Doctor try to do?

I would love to defrag my hard drive my can’t because of these errors.