About the backup file, It is not a "Windows" component, I don't know what created it, but I don't think there is any way to restore it, and I doub't you will have any call for it.
On the .dl entry
What you need to do is run regedit and click on
+ HKEy_Classes_Root
Then scroll down to the 'd' entries look for
.dl
I can show you an attached picture, but you will not see that entry, just .dll which you do NOT want to delete.
.dl (with one L) should be right next to it. It may look like this:
.dl_
Possibly the underline was not displayed in the attached text copy of the startup log, but that is usually the way it is found
If you can't find it. I wouldn't worry too much about it. Legitimate programs will sometimes place that as a part of the install process for their dlls but not really use it after the install.