How can I reset my Admin password on a Mac.

I recently reset my Admin password and must have done a
typo (late in the night). Now I can’t access it. I have tried
to restart using my install disk without success. Can anyone
please discribe how to use the Netinfo Utility
mentioned in greater detail. Also, is there any other
way to reset it?
Please let me know with specific details, as I do not want
to screw this up and a comment: One can also boot
into “Single-User” mode by holding down cmd-S at
startup. Please man sudo, and please be careful: you won’t
get a second chance” is scaring me!
thanks!