Can someone help me. I need to change the username validation too only check for numbers. The current validation requires you to enter alpha characters as well.

I want my users to only enter numerics for there username.

Check comprofiled.html.php for RegExp and remove the A-Za-z part leaving only 0-9.
This would also affect password field so if you don't like this create anonther regexp only with 0-9 for user name.
You should also edit the VALID_AZ09 in language file for info tip.

i wanted to remove the user name validation , but by editing comprofiled.html.php , did not work ...

I made a typo.. It's comprofiler.html.php the file you should edit.
var r = new RegExp .... (found in several places according to joomla version you have)

and the check is done with
... if (me..value == "") {
section r.exec(me..value

assuming you use CB1.1
In CB1.2RC4 it's editable from the backend...

I hope that would help.