MSVCP120.dll is the C++ standard library from Microsoft's Visual C++ 2013 package. Programs built with Visual Studio 2013 need it to start, and the usual "was not found" message means the 2013 redistributable was never installed on this PC, or an uninstall or cleaner removed part of it.
vcredist_x64.exe and vcredist_x86.exe. A 32-bit program needs the x86 package even on a 64-bit PC. Restart the PC when done.Look inside the failing program's folder for its own copy of MSVCP120.dll. Some programs ship a private copy, and if that copy is older or damaged it overrides the healthy system one. Rename it (add .bak) so the program falls back to the system DLL, then relaunch. If only one program fails while others work, that program is damaged, and a clean reinstall is the remaining move.
What is the difference between MSVCP120.dll and MSVCR120.dll? They are two halves of the same 2013 runtime. MSVCR120.dll is the C runtime, MSVCP120.dll is the C++ standard library. Both arrive in the same redistributable, so installing it fixes both errors at once.
Do I need both the x86 and x64 packages? Yes, on a 64-bit PC. 32-bit programs use the x86 set and 64-bit programs use the x64 set, and you often cannot tell which a program is until it fails.