http://www.microsoft.com/windows/ie/.../oe/setup.mspx

Go to the part that tells you how to add email accounts. You will need to know what email protocol your isps email server uses. I am guessing you already do, because you have email comming in already. I dont really understand how you got both email accounts set up at the same time on the same computer, theroetically you should have gone through the add email account process twice for both x and y on both computes.

http://www.microsoft.com/windows/ie/.../oe/setup.mspx
go here to learn how to delete an email account from outlook