Security with server on my computer-new questions
In the "Database Driven Website using PHP and MySQL" book, it tells how to download Apache, PHP, and MySQL for your own computer. I am using XP Pro. I understand an outsider could access Apache or IIS by using my IP address. Hackers use IP addresses, not URLs. It seems to me I would be inviting these hackers into my computer by having a server on my computer. XP can be used to host an Intranet using IP address (up to ten stations). My ISP, using Apache, tries to block hackers, but many get through. Could I block them by simply using my firewall and block Apache from accessing the Internet???? Is there a better way??? Or, is there some technical issue that would prevent me from doing this???? (I am not a server tech, obviously.) Please, not a "basically, no" answer, but a more technical answer. I like to know "why not?".
Thank you very much.