I have some sympathy with both your ISP and Fujitsu.
Your ISP is responsible for getting their signal to your house which they seem to have done, and Fujitsu is responsible for providing a working laptop which they have done.
If you have chosen to set up a wireless network then I am afraid that is your responsibility.
(Not wishing to be hard but trying to see it from their point of view).
Here is a short article that may help you set up your wireless network:
http://www.microsoft.com/windowsxp/using/netwo rking/setup/wireless.mspx