Booting under a user login

[Victor]

I succeded in convincing my wife to use StartOffice for her work abandoning 
M$ Word. 
In order to make it easier the access to a user login to a newly acquired 
absolute beginner to linux, I'd like to set her PC's boot up so that it 
goes automatically under a certain user login (I mean without being 
prompted for a username and , possibly,password).
Is that possible and, ABOVE ALL, how?
Ciao
Vittorio