The mark-up for the HTML page is
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<title>Query String Link Example</title>
<p><a href="welcome1.php?name=Kevin">Hi, I’m Kevin!</a></p>
The link is a "relative" link (as opposed to "absolute" like your type into the address bar).
Because its a relative link and you're going to it through your OS it looks for it as a "file" instead of "http".
Because you're getting
I'm guessing you put the file directly under the WAMP app folder instead of under the htdocs folder.
When you sart up the server and go to a localhost HTTP address, it does NOT look in the main WAMP app folder, but goes directly to the htdocs folder.