Your file is right, so I'm guessing your email is not set up properly. Go to "Admin Options" then "E-mail Server Configuration" and make sure "E-mail Mode" is turned on and that the other fields are filled out. Then test your email my using the "Send Topic to a Friend" link at the top of the Topic page for any topic in your forum. If the email doesn't arrive, you've not configured the "E-mail Server Configuration" settings properly. Once these are right, you should be in good shape.
One other thing to note - you've set up the file to notify you of people only if email validation is turned on, but restrict registration is turned off. If you want notification when restrict registration is turned on as well, you need to add those same lines after the code that reads: if strRestrictReg = "1" then
Response.Write " <p align=""center""><font face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """>The Administrator has restricted registration on this forum. You will receive an e-mail as soon as the Administrator approves your request.</font></p>" & vbNewLine
(i.e. before the "else" line)