domain access

i have a laptop with xp pro and two companies in diferent places which they have different domains. i want to configure my windows logon to show me both the domains so i can choose the domain of its company every time im moving from the one company to the other so i can have access to my servers files .i don want to have acess to the two domains at the same time just the choice at the windows logon for the two domains

thanks in advance