It might be useful for a newbie to understand that it is very easy to enable the IIS webserver on your own Windows computer. The problems are:
Speed. Home internet connections do not usually have enough bandwidth to handle much traffic, but this is not a problem for most people's personal sites.
Legal. Most ISPs including most broadband providers do not allow customers to run services such as web hosting, ftp, etc from the ISP connection. I've never been "caught", but I've had plenty of friends who have been warned to by their cable company to turn off their web server.
Reliability. If it is important that your visitors can reach your site at all times or during business hours, your own home Internet connection is not as reliable as a professional hosting company. This is because a hosting company usually has multiple, redundant, high-speed connections to the major Internet backbones. They also have power generators to keep their network running for days during power failures.
Now, if you are simply learning about webhosting and building websites and scripting such as ASP, then by all means, don't waste your money on a hosting company. Keep building on your own computer until your needs and experience grow. Most likely your ISP will not notice or care unless they notice a lot of traffic on your end.