Do you mean QV.exe? See available list of parameters in in "Help" / "About QlikView" / right click on bottom logo. You can use "MaxCoreMask*" for core usage restriction.
You mean a single installation on a single machine? Then you will need try the suggestion from Andrei Popkow or change hardware-setting within the BIOS and/or system-settings in your OS - but in this case you should very well know what you are doing.
But maybe your problems (which?) are more connected with the working-set settings and generally it's recommended to use none other tools parallel to qlikview on one machine. From the points of costs and effort it could be the better way to use (buy) several machines.
