Its not as easy as it sounds, well it is, but it isnt.
You'll need a very fast connection, check your upload speed.
Then download PHP Triad (search
www.google.com - always in the top 5).
Get your client ip by right clicking on your ISP Connection in ya systray, write down client ip.
Then any file in C:/apache/htdocs
is
http://[yourclientip]
Thats just the simple way, if you want to turn it into a web server so you can use .com's... thats a different matter and i wouldnt attempt it with no knowledge about this.