In the My Account settings at the top of this page make sure the web page feature for the account you want the web pages associated with is enabled.
Save all of your html files and supporting images, etc from Earthlink to your work station using an ftp client. It can also be done with a web browser but would then need to be done for each individual page.
Make sure your main page is named index.htm or index.html. There are some other names that can be used as the default page but index.html is the most common. The server is case sensitive and Index.HTML for example would not work as the default main page.
Use an ftp client to upload your html files and supporting images. Upload to upload.comcast.net Your username is your email address without the @comcast.net. The password is your email password.
I don't know about keeping domain name. It depends on where it's registered. You should be able to just change the redirection if it had been pointing at earthlink and now needs to point to comcast. Describe your situation.
You get 1 GB of space. If that's not enough, you can probably have some of it on a secondary account's space.
Realize in this switch that you cannot use any server-side scripting. If you need to turn on executable permissions on some files, that won't work. You may be better off going with an inexpensive web hosting service. I have my business site at FastURL.com, but there are many less expensive such services.
>How much space does comcast allow for a free website and can I have two different websites....
Comcast allows 1 GB web space per email address. You get 1 primary email account and 6 secondary addresses for your account. If you establish all 7 email addresses for your account you would have 7GB web space with 7 different web addresses.