wifi-access question

[Tobias]

Please don't laugh... this question may sound quaint and naive:

I'm only now getting ready to use airport in my iBook - I'm not in my new
place yet and don't even have a base station yet. But this morning I got
itchy and turned airport on just for the fun of it. Ta-da! A signal, about
50% strength, of a network named "ais"; must be somewhere in my
condo-building. But I couldn't log in - is it because the owner has
restricted the access or am I doing something wrong... ?

Also: Later this spring I will have another computer (Windows) moving into
my household - should I buy the Apple airport station or is there another
recommendation?

Many thanks,
tobias.