Disk Doctor won't allow me to repair

[boynigel]

i have a G4 running tiger that's been buggy lately so i ran Disk Utility. i got this message:

Invalid node structure
The volume Untitled needs to be repaired.

Error: The underlying task reported failure on exit


1 HFS volume checked
Volume needs repair

fair enough, but the "repair disk" button is low-lit, not allowing me to repair. now what?

 

[burnout8488]

Try booting into single user mode (command-S) and running "fsck -fy".

I think that's the proper way to go about it, someone correct me if I'm wrong.