A few questions for you:
What kind of internet connection do you have?
Do you have a router between your computer and the internet connection?
Will you be registering a domain name for use with this web server?
What kind of content do you intend to serve up with this web server?
Have you thought about which server you want to run? (Apache, IIS, lighttpd...)
Unless you are serving up large files, it doesn't really matter which hard drive is being used.
The database on my server uses the most space, but all of the content is < 500MB.
As for installing 7 to a 2nd hard drive, would you still be using both drives in the same computer? If so, there really is no purpose for doing that.