Programs and applications often require other files to be present on your computer, but sometimes this isn't the case. DLL stands for Dynamic Link Library and these files are used by many programs including games.
MSVCR100.DLL is a Microsoft Visual C++ file and is required by applications which were made with Visual C++. This includes many apps, including games, media players and more. It's annoying if it's missing from your computer, but it is relatively simple to fix.
How to install msvcr100.dll
The official way to install the file is to get the Visual C++ update from Microsoft.
The latest version can be found here on Microsoft's website. It includes both the 32-bit and 64-bit versions, so you don't need to know which version of Windows your computer has.
Click the Download button, then tick the files you want to download. Again, if you're unsure, tick them all.
Click Next, and the appropriate file for your computer should automatically be selected. Depending upon the browser you're using, you might get options to save the file, or run it.
If you only see a 'save' option, pick a location to save the file, then run it. If you can run it directly, do that.
When you run it, User Account Control will ask for permission. Grant it, and then you'll see a window like the one below. Either install the package, or choose the repair option if a version is already installed.
Click Next, then Finish once the process is complete.
Now, restart the app or game and it should now run without throwing up the error.
Another option is to search other computers you own to see if the msvcr100.dll file is present. If it is, you can manually copy it to the C:\Windows\System32 folder - this assumes you have used the default hard drive letter for Windows.
If you're running 64-bit Windows, also copy the file to C:\Windows\SysWOW64. (If that folder doesn't exist, you probably don't have 64-bit Windows.)
Launch the application or game that caused the error, and it should now run - or complain that another DLL file is missing. If it still asks for the same file, try rebooting your computer and if that doesn't fix it, then copy msvcr100.dll to the application or game's installation folder which could be in C:\Program Files or C:\Program Files (x86).