First thing to understand is that the only thing telling your computer that SOLIDWORKS is networked or standalone is the serial number. Usually a network serial number starts with 0010 and a standalone might start with 0000 or 9000.
To change your installation from network to standalone or the other way around, just change the serial number from Add/Remove programs (winxp) or Programs and Features (win7).
Go to the Control Panel and select either one of the two depending on the OS. Then select SOLIDWORKS from the list and click Change. The installation manager will start up and you will need to click through all the screens even though nothing is being installed. When it prompts you for the serial number just change it to the new one.
Computer Aided Technology, Inc.