I have the following problem.
I have downloaded a web page with the wayback machine downloader. This web page contains query strings. The wayback machine downloader does not save this as ?= or id= etc. but as %3f or %3d. This looks like this:

When a query string is called up, e.g. splash.asp?page=3, nothing happens. The same page always appears, no matter which query string. I use IIS for hosting. 

With kind regards

This post is old, but I wanna answer it in case someone else is wondering.
 
ASP (like PHP) is a server-side scripting language.  When you visit an ASP page with your browser, you will only get the HTML output from that ASP page.  The Wayback Machine gets the same HTML output when it crawls a website.
 
The query string is not part of the file name.  In order to allow you to download these as separate files, the WBM encodes the question mark as well as the special characters in the query string so they can be part of the file name.
 
Renaming them is not an option (the decoded query string can't be part of the file name).  Even if you could, that wouldn't allow a link to "splash.asp?page=3" to work, as it requests splash.asp (passing it the parameter "page=3").  Supposing that the WBM also saved "splash.asp" without the fluff, it still wouldn't know what to do with the parameter; you'd need the original document which has all the parameters and variables defined, which nobody can access or read except for the server it originally resided on.  The files in your screenshot are nothing more than static HTML files at this point.
 
You really only have one option:
1) give the files a name that's more meaningful to you (without special characters)
2) update the links inside the files