The difference between the .dll and the .dl_ files is that the "_" indicates a zipped "source" file that normally would be copied directly from the installation disk.

The .dl_ file "unzips" to produce the .dll, but in some cases the initial .dll needs to be "populated" with information specific to the installation - usually handled by the installer; but often just rebooting, once the .dl_ (or an unzipped .dll) is present, will finish creating the final .dll.

To find an "original" .dl_ file you have to look in the .cab files (the actual installation source files). Search engines in various Windows versions vary with respect to whether they'll tell you if the .dl_ actually is present in the .cab files, unless you search directly in the xxx01.cab file.

A "default" installation of most Windows versions would put a copy of the .cab files on the hard drive, so that you don't need to insert the installation disk during updates or to change options; but disk cleanup allows you to delete those "to save disk space" and lots of people wipe them out by accident, or intentionally without realizing that they can be helpful.

The file in question appears to be used only for database applications based on the mostly obsolete "Microsoft Jet" database structure, although I can't be sure of this. As for many "obsolete" components, live descriptions are somewhat vague, but it appears that the only problem likely without a correct version of the file might be failure of a very old version of Microsoft Access. Some info at Wiki: Microsoft jet

In database applications of the file, even later versions/updates of Access apparently renamed the file, and it's common for a more current database application to use a "diferently named" dll. Win2K would still attempt to install the original, but a newer db - possibly even an updated Access - will probably use something else anyway.

It appears that you can pass on the computer with a clear mind, and further concern would only be to satisfy your curiosity - if any remains.

John