exactly... also you should convert it to int (unless it's impossible with the data).

Also even some have disagreed about this I've seen a huge speed improvement in changing my primary keys from char(6) to int on a orders table (yup crappy set-up but I can't change it). I simply copied the data to a new column of type int and moved the clustered index there. In this particular case I've seen speed improvement of 50%-75% on queries that are run 1000s times per day.