Sorry to say that DotNetNuke requires the IIS webserver which is only avaliable on server and pro versions of Windows. Do you happen to have a Pro version of Windows XP arround? Or better yet, a Windows 2k or 2003 server? One limitation with IIS in Windows Pro is a that it allows up to 10 web connections at the same time, while Windows server has no limit.
As far as the database goes, DotNetNuke is designed to use Microsoft SQL Server databases. eg. MS SQL Server 2000 or 2005, or the free Microsoft SQL Server Express 2005 version which would probably be your best bet as a replacement to MySQL.
I also used to use PHP-Nuke, and for a long time, I used to think it was the best thing arround, until I setup DotNetNuke and noticed all of the things that it could do that PHP-Nuke either could not to, or was a whole lot harder to modify things in PHP-Nuke than DotNetNuke.
Also, PHP-Nuke requires you to pay for membership to download the newest version, while DotNetNuke requires nothing which makes it a true open source application.
Let us know if you can get your hands on a Pro version of Windows XP or 2000 and we will help you get it setup.
Good luck,