Vista camputer suddenly disconnects internet

Hello,
I have two laptops connected wirelessly through modem. One running under xPro -never ever has problem with internet disconnection and other running under Vista Home has every day mentioned problem. Sometime I get my Vista PC immediately connected after startup and connection is fine until approx. 1 hour than suddenly disconnect. Most of the time I have to wait for approx. 1 hour, after start up, to get internet connection....!!!???
Having all checked - viruses and similar stuff, having consulted my internet provider, noting found wrong!
Question is:
When Vista computer is started, usually but not always I have no internet connection, only after one hour or so... At the same time if I switch on my xPRO computer internet is immediately available!?
So what is wrong with Vista Home computer?
Regards & thanks,
Ray