Disk Verifying error... Should I reformat and start again?

I was trying to run bootcamp to partition my hard drive, I have done it before but simply took it off because I ran out of space on my hard drive to run both osx and xp. So I went to partition it to put xp back on, and bootcamp assistant says that it cant partition it and to use disk utility.

So, after verifying the disc, it comes up with the following...

Verifying volume “Duncan”
Checking HFS Plus volume.
Checking Extents Overflow file.
Checking Catalog file.
Checking multi-linked files.
Checking Catalog hierarchy.
%)
Checking Extended Attributes file.
Checking volume bitmap.
Volume Bit Map needs minor repair
Checking volume information.
Invalid volume free block count
Invalid volume free block count
uld be %@ instead of %@)",2)
10077864
10077489
The volume Duncan needs to be repaired.

Error: The underlying task reported failure on exit


1 HFS volume checked
Volume needs repair


What the hell does that mean?! I have an external hard drive so i'm very tempted to just backup everything that I need, and then reinstall osx fresh and put xp on there also..

Can this be fixed easily?
Is it worth starting again?
If so, how would I go about backing up? Is it a simple copy and paste to the backup drive?

Thanks