Since posts that ask members to "name a cheap registrar" are invitations to promotional spam-a-thons we don't allow such Q & A sessions. Sorry, but it's policy for good cause.
You can easily query most search engines for "cheap domain names" or "cheap domain registration" or similar phrases and lots of advertisements will appear. Just not here, though.
Hope we can be more helpful in the future.
You might want to take some time to read the following whilst you're working up the courage to ask your next question. ;0)
Domain Forum Charter [webmasterworld.com]
WebmasterWorld TOS or Terms of Service [webmasterworld.com]
Thread about promotional posts in forums [webmasterworld.com]
Guide and resource for new members [webmasterworld.com]