Using the "start" command with parameters passed to the started program

START has a peculiarity involving double quotes around the first parameter. If the first parameter has double quotes it uses that as the optional TITLE for the new window.

I believe what you want is:

start "" "c:\program files\Microsoft Virtual PC\Virtual PC.exe" -pc MY-PC -launch

In other words, give it an empty title before the name of the program to fake it out.

Instead of a batch file, you can create a shortcut on the desktop.

Set the target to:

"c:\program files\Microsoft Virtual PC\Virtual PC.exe" -pc "MY-PC" -launch

and you're all set. Since you're not starting up a command prompt to launch it, there will be no DOS Box.