In an install command, it needs to detect and treat the program to be executed differently than the command line parameters to be passed to that program.  That means it MUST be able to identify the space that separates the two.  So, if there is a space INSIDE the path and name of the program to be executed, then it MUST be quoted.  No quotes should be used in the rest of the command line.  So, consider the following example: I want to execute the program:  \Program Files\My Test\myprog.exe And pass to it the command line parameters:  \Program Files\My Test\myfile.dat -C The command I would use would need to be: "\Program Files\My Test\myprog.exe" \Program Files\My Test\myfile.dat -C It would see the quotes and treat the entire quoted string as the program to be executed.  The remainer of the command line after the space following the quote would be passed as-is to the program executed.  This is consistent with what you would have to type at a DOS prompt to get the same result. Without the quotes, it would try and execute the program:  \Program and pass to it the command line:  Files\My Test\myprog.exe \Program Files\My Test\myfile.dat -C which is clearly NOT what you want. Any other form of quoting WILL NOT work.  You can ONLU quote the ENTIRE path and name of the program to be executed and only using double quotation marks (e.g. " " ).