Network Mapping issue!

I have a laptop that is connected to the network, it works fine (xp home by the way) just periodically it will just randomly forget the username and password login to connect to the network shared folder?

This is a HUGE problem and need some assistance!

I would have to disable mapped network drive and reconnect, then re-enter the username and password! When I do that there is no check box to tell the computer to remember the password and login name...