There's two parts to this question: can you technically, and can you legally? Let's go with the "legally" first.
It all depends on your DSL providers' terms of service. Some of them will allow for hosting your own personal, individual site. A few more *may* allow you to host a small business site for your home business. Almost none will allow you to run a commercial web host out of a room in your home, or off of your PC.
So: can you legally host web sites from home? Check with your upstream providers' terms of service.
Now, on to technically.
You're running Windows, which is not an operating system that I have used as a web server. I think that they've got some home server pack. Check their site for more information.
Now, on to some depressing but necessary questions:
* do you know how to install and maintain a firewall?
* do you know how to monitor and block hacking attempts?
* do you know how to run a mailserver?
These are part and parcel of being a web host. Windows has tried to sell people on the idea that you just install any software of theirs and BAM you can do anything - but there are still some tasks that require a little more background knowledge.
If you're really interested in this, you might check out some courses at your local JC or university on Windows web server administration (make sure that they're web server courses, though - there are servers that don't connect to the Internet, and they work a bit differently). They'll give you what you need to get started.