My card or router is rated for up to 300 ft or yds? can't remember which.
A lot of the signal strength depends on if it has to go thru walls, wall type, indoors or outdoors that sort of thing.

for winXP - using encryption settings-
In your network connection settings go to-
/properties/wireless networks/preferred networks/click any networks on the list and then/properties/you can set WEP {weakest} or WPA{mid} or WPS-PSK {higher} for encryption {depending on your card/setup}.

Or you can let a security software program handle this.

I live out in a rural setting so I don't have any other networks or hot spots other than our own computers to worry about.