The easiest way to test if it is working, would be to visit
http://localhost. You should get an Apache default page. If you go to
www.whatismyip.com you can check your IP address. If you tell others to visit
http://thatipaddress they should also get the page.
IIS is generally easier so if you can easilly upgrade to XP Pro, it might be worth doing if Apache doesn't seem to work.