how to edit Units ?

i am beginner to learning blender i use version 2.48a i have some question about to edit
Units on blender . Where is menu i can to edit or change Units to Metric, Us Standard ?
:confused: how to use it ?

I hate to break it to you, but that features being added in blender 2.5, you should just assume that one blender untit == one foot or one meter.

ok. i understand
thank you :smiley: