One router, four computers: potential problems?

Hi, This is probably a really basic question, but I'd appreciate any advice/feedback. We now have three computers in our house--our Dell Dimension desktop, my son's HP laptop, and my husband's laptop, which he uses for work (he works from home.) We have all three linked through our D-Link router and the modem from our Internet provider. I have Network Magic running on the desktop, which allowed me to set it up so it recognizes the two laptops and they can share the printer (I'm not sure if Network Magic is actually necessary--it came with the laptop.) We just ordered a Dell Inspiron laptop for my other son, and I'm wondering if the router will be able to handle a fourth computer without a sacrifice in signal quality. Our house is not that large and so far all three computers get "excellent" signals. How many computers can a router typically handle in a home? I doubt that all four would actually be running at the same time most of the time. Are there any other potential problems I should be aware of? Thanks! PS I guess I should add that the modem is a cable modem and that the three computers we have now all run Windows XP, while the new laptop will have Vista. I hope that the router will not have a problem with a Vista computer--as I understand it, it shouldn't be affected by a particular operating system?

Message Edited by kpj824 on 01-06-2008 07:37 PM