DLL (Dynamic Link Library) files are basically “support” files for certain types of software. They are generally (but not always) found in your Windows System directory.
They work like this: Let’s say a program needs to perform an operation. Rather than all the coding being built into the program, it uses a particular DLL file that, with a simple call, can perform the operation for it. Saves lots of programming time, especially since many of the common DLL files are already installed with Windows.
I’ve also had lots of people ask about deleting these files. Well, the best advice is not to, since many of your DLL files are used by more than one program. Going through and deleting the ones you *think* aren’t being used anymore is a lot like getting under the hood of your car and yanking wires that don’t look important.
If you’re really concerned about stray DLL files, make sure you run uninstall programs. Most programs include an uninstall program that will (should) take out all the extra DLL’s. It’s not foolproof, but it’s better than playing guessing games with your DLL’s).
If you manually remove a DLL file during an uninstall, it may be shared by another program, so when you run the other program, you will receive a missing file error message.