keeps frezzing

ok i am on my school ibook g3 800mhz and lately i have been having this problem where it keeps on frezzing on me like i can barely get to my desktop i will probably be lucky if i finish this thread, but as far as is there anything i can do like the windows scandisk i dont know. or is my hdrive about to crash.

Reboot Computer
Hold down Apple and S as soon as it turns on
This will boot into Single User Mode
When the Unix Mumbo-Jumbo is done loading up type in
/sbin/fsck -f
And hit enter
This will repair the File System
If it corrects something run the scan again to make sure everything checks OK
When finished type in reboot and hit enter