2
Well...you'll need to set up a web server and minimally have MySQL and PHP installed on it...
IIS is a popular web server app...and there are windows and apache flavors
here's a link to a how to set one up site:
http://www.webmasterstop.com/cid_11.htmlAs for migrating the site....check the FAQ's for specifics, but you just need to dump your database, and copy that over to the new server...and then edit your mainfile.php to reflect the new servers information for root path, and database info.
Hopefully you have good 'upload' speed on your DSL connection, as your site will be slower than molasses in the winter on the standard 128k up rate most DSL providers offer (approximately twice as fast as a 56k modem, spread out amongst ALL of your users)
FYI: Good upload speeds can be purchased, but are costly. I pay close to $60/month on top of the regular monthly fee for guaranteed 512k minimum, and a max of 'up to' 1.5Mbps