Can't reboot back from Vista to OS X

Hi there. I'm totally newbie in Mac world and want to ask for help in my small (I'm sure for you-very small) problem: after the upgrade of Mac OS X into Leopard and trying to solve the audio driver (Sigma Tel) problem in Vista by running Boot camp setup in Windows (now I understand - that was wrong - I should have limited the setup to only audio drivers), I can't find anymore boot camp restart into Mac. At the same time my WiFi connection to my home network (in Vista) had been lost and I don't know how to correct that issue. Please advice.

Thank you.