Vista - How to remove Old IDs

Hi:
I changed to Vista from XP due to XP burned-out.
On Vista, I created a brand new ID by accessing 'Uer's Account' < Control
Panel < Settings.

When I looked at 'Users' by accessing;
Computer < Compaq C: < Users

Names of old IDs are still there, not to change to a new ID I created after
having switched from XP to this machine with Vista.

My question is;
How to remove old IDs and make my brand new ID on Users?

Thanks for your help in advance.