I would recommend checking your connection string to make sure that you've also edit the comment tags so that your connection string edits are not considered comments.

Operating System, I think the lack of help so far (other than the valiant attempt by eck two) may be due to the fact that other than that it's not working, we don't really know anything else. First, you mention a "Runtime error". What is the message? A screenshot would be great or copying the text - otherwise, we're looking at a few million different reasons for an unspecified "Runtime error". While the authors of the books certainly appreciate that you spent $$$ on videos and books, that's probably not the cause of the problem (and didn't solve it either)  We need to know what problems exactly you are running into to offer any useful help. Otherwise, we'll just think, there goes another Operating System trying to run applications - must be Windows based (sorry, I couldn't resist that lame pun).

If you do try it again (and DNN is certainly worth the effort), make sure to clear the database completely first. Reusing a database after a failed install has brought me nothing but trouble. Also, maybe you could consider using an ISP that offers a simple "one-click" DotNetNuke application installer. A fair number out there offer this (google), maybe they're not on the latest version, but as in my case, it offers valuable experience with a simple, working installation, which you can then apply to your own install from scratch. I'm merely mentioning this approach as this is how I "stumbled" into DotNetNuke, I was just trying out my ISPs application installer which installed DotNetNuke (and have yet to regret it).