Before you Delete, Load Outlook Express (OE), Click on Tools ---> Accounts. On the window that opens, hit 'Mail' at the top. Hit properties. Copy ALL the information under the Servers Tab.
Then hit cancel. Select your account, and click on 'Remove' to delete the account.
To make a new account, click add --> Mail (This is all under the 'Accounts' Menu). Then input the information, as asked, using what you copied earlier.
Who is your Internet Service Provider?