ok i have gone through a tutorial on rigging a biped )my first by the way!!!), but i think i did something wrong the mesh gets messed up kinda when i move the bones. i will post pics of it when someone answers plz!!!

You messed up on the vertex weights and need to change them up to be more realistic.
Maybe...
But it would be much easier to give advice if you actually gave us pics.
Edited by Enzo03 on Feb 20, 2008 at 06:40 PM

Import an animation to help you find where you need to fix vertex weights
In the Skin modifier,
click the Edit Envelopes button,
select a bone,
mess with the envelopes, the spherical things around the bones in the viewport. They help pre-set vertice weights, but you'll probably need to manually fix some weights anyway
select the verts that aren't moving with the bone like they should (after playing the imported animation), and
set Abs Weight to 1.
If some verts should stretch between 2 bones (like skin, unlike armor),
select the other bone and
set the vert's weights to .5 or other

If you can get it to work right, the Skin modifier's Mirroring thing can cut your work in half

this site shows how to put the bipeds on halo right?

If you wanted to rig a half decent biped then you shouldn't rush it, take your time.