how to mod rewrite the url when the user registers

loginname,url

[sunilkumar]

hi,

I had a small requirement of mod rewriting i.e when the user registers to my site using the registration form then after the registration is successful then he should redirect to this url like

username.mysite.com
or
mysite.com/username should point out to his profile page

any suggestions pls,I need it urgently

thanks and regards,
sunilchai