Do you have an anti-virus program? Or another instance of the .exe running?
The error is, as @DanM pointed out, that the .exe file is already running. I recognized it immediately because I get the same error all the time myself!
Tip: It’s a linker error, not compiler error. Visual Studio is pretty neat when it comes to the error codes, if it starts with LNK it is the linker complaining. If you check out this page on MSDN, you can read more about the process of compiling and linking when building your program: https://msdn.microsoft.com/en-us/library/91621w01.aspx.