Disk utility error

i noticed that my computer was having occasional hiccups when running multiple programs. i immediately ran the disk utility and tried to verify the disk. it came up with an error saying:

incorrect block count for file Steam_2011_09_18_14_02_16_833.mdmp

(It should be 0 instead of 13)

then a few other messages stating what it was checking then at the bottom it reads:

The volume Macintosh HD needs to be repaired.
Error: Filesystem verify or repair failed.

its been bothering me and i would appreciate any help
thank you

G'day and welcome to the forums.

You need to boot from your system disc or Recovery in the case of Lion, and go into Utilities > Disk utility > Repair Disk.

Helps enormously if you provide computer and operating system details.