I am "trying" to use Hotmail exclusively but my address as sent to others is my old Outlook Express one, NOT my Hotmail address. This is causing endless confusion. Help!

Have Outlook Express up and running on XP PC, but use only as a backup.  Primarily using Win7 on newer PC and Hotmail (or is Hotmail just another name for Windows Live?  Or the reverse?  Everything sent from from Win7 PC (Hotmail) appears as though it was being sent from OE and has old e-mail address, which causes endless confusion as return mail is not coming to this PRIME Hotmail Address, but to OE on backup PC.