You cannot have more than one account.
User names can be changed but only if you have a legitamit reason why you need it to be changed.
There are so many members here. If the mods changed everyones username who grew out of it, moved, or didn't like it anymore they would be very busy.
PurseXaXholic is right. You are not allowed to have two accounts.
Vlad is the only one who can change usernames. If you pm a mod they will tell you that same thing.
I have been told that Vlad receives many requests every week for changes and almost none are approved. The reason being that with over 200,000 users it would be a nightmare to try and accomodate every one.