Windows cannot open DLL files?
If Windows is unable to open DLL files you may not have the appropriate program installed or may have a registry related error.
Open DLL File
Dynamic Link Library Appropriate program for file extension DLL: DLL file is a file shared between a number of software programs (and are similar to .EXE files), used in Microsoft Windows and OS/2 operating systems.
These files will contain compiled procedures, or drivers (for example for a printer) which a range of programs can then all access. You will often come across DLL files in the context of not having them, which is to say if you plug a new piece of hardware into your PC the computer might complain about missing the 123XYZ.DLL file.
In practice this means that the system cant find the driver associated with this hardware. You will usually be able to download legitimate DLL files from a CD accompanying the hardware, or off the Internet from the hardware producers website.
Additional comments: It is unlikely that you should ever have to open or edit these files (unless you are a specialist). Also note that these can be a source of infection and should be saved from the Internet or executed from an email, with care.
Specific software that can open DLL file include: Generally there is no need to open it and it isn't particularly advisable to attempt to.