How do I launch a program from command line without opening a new cmd window?

In Windows 7+ the first quotations will be the title to the cmd window to open the program:

start "title" "C:\path\program.exe"

Formatting your command like the above will temporarily open a cmd window that goes away as fast as it comes up so you really never see it. It also allows you to open more than one program without waiting for the first one to close first.

Add /B, as documented in the command-line help for start:

C:\>start /?
Starts a separate window to run a specified program or command.

START ["title"] [/D path] [/I] [/MIN] [/MAX] [/SEPARATE | /SHARED]
  [/LOW | /NORMAL | /HIGH | /REALTIME | /ABOVENORMAL | /BELOWNORMAL]
  [/NODE <NUMA node>] [/AFFINITY <hex affinity mask>] [/WAIT] [/B]
  [command/program] [parameters]

"title"     Title to display in window title bar.
path        Starting directory.
B           Start application without creating a new window. The
            application has ^C handling ignored. Unless the application
            enables ^C processing, ^Break is the only way to interrupt
            the application.

Just remove the double quote, this works in Windows 7:

start C:\ProgramFiles\folderName\app.exe

If you want to maximize the window, try this:

start /MAX C:\ProgramFiles\folderName\app.exe

Your command START "filepath" will start a command prompt and change the command prompt title to filepath.

Try to run start /? in windows command prompt and you will get more info.