Issues with Time Clock on Exchange Server

Ok I have installed Windows 2003 Server with all updates and Exchange Server 2007. When I reboot the server the time keeps chaning and then my services will not start becuase the Exchange is more then a few minutes off from the DC. It is reverting back to an AM time frame. I have searched all over google and cannot find resolve to this issue. I know that the time zone is correct what am I missing!!!!

Thanks,

Jenn