The exact procedure depends on what email client you are using. Generally, if you go into your account options, you can change your displayed name that is sent with each message. This won't change details of your actual email address which will still be available to the recipient.
As you talk about an administrator , it sounds to me as if your email address may be networked . If so , then the display name can only be changed on the network server .........you will need password etc .
If your email address is ??? @eircom.net then you can click on '' start - run - 'type in '' inetwiz , click Ok and follow the prompts .
If you have a gmail, yahoo, hotmail etc , then you need to edit your account information