When you try and click on a .log file served from IIS6 you receive a 404 error.
You need to look through you log files and find out exactly what 404 IIS was giving. If it was 404 with a sub status of 3, then it is denied due to MIME Type, so make sure to add a .log/bat MIME Type at the website/vdir level and it should immediately be downloadable.
You can add the .log extension with application/octet-stream in the MIME types.
However, if that vdir has “Scripts and Executables” enabled and a Scriptmapping for .bat, then you will likely see 404.2 — in which case, you need to remove the Scriptmapping so that downloading is allowed.
If it returned 404 with a win32 error of 2, then that’s a real “file not found” — look at the vdir mapping to make sure the file actually exists where you think it does.