wireless connectivity issues

I am running Vista Home 32bit and my computer (laptop) will not recognize my wireless router. It tells me that I have limited connectivity and no internet connection. My wifes laptop picks up the signal fine and has no issues. Service provider can't help, manufacturer can't help. The really weird part is that I check to see if I can pick up unsecured signals and it works every time! What do I do?

Try first to reset your tcp/ip:
Run CMD as administrator
Type in: netsh int ip reset
Press Enter
Reboot.

Thank you for the help. I figured out the problem. It was as simple as downloading service pack 1. I thought my computer was already downloading updates automatically but that's what I did and no problems since. Thanks again for the advice!