Key

$ = 1-49 USD
$$ = 50-99 USD
$$$ = 100-200 USD
$$$$ = more than 200 USD

Notes:

1. PWS is for Windows 9x machines only. Do not install this if you are running Windows NT 4 or Windows 2000.
2. I know it's the NT option pack. If you run the Windows NT Option Pack on a Windows9x machine, the Option Pack will recognize that this is not an NT OS and will install PWS instead of IIS. Wacky, yes, but it works. Instructions are at http://www.asptoday.com/articles/19991214.htm
3. IIS comes bundled free with Windows NT 4, Windows 2000, and Windows XP Professional. If you have not already installed it, simply search for "IIS" in Windows Help & follow the instructions. If you are using Windows XP Home, you'll need to follow these instructions for installing it, which are long and complicated. Also, note how this article compares the ridiculous ease of installing a Web server in Mac OS X with the struggle you must go through with Windows XP Home.