You are welcome to run any number of simultaneous instances of RealTest on the machine(s) for which you have activated your license.
Each instance everything that it needs to run scripts in its own allocated memory, so they will not collide or conflict with each other in any way.
The only possible exceptions to this are:
1. The realtest.ini file, which is used to remember things like window positions, default settings and recent file lists, is automatically saved when RealTest is closed, so whichever instance is closed last will be the one whose settings etc. are saved in realtest.ini.
2. Similarly, if multiple instances are running the same script file, the file saved to disk will be the one from whichever instance has run it most recently. (Scripts are always automatically saved before they are run.)
You can optionally copy your entire RealTest folder to one or more other locations on your disk drive, in order to avoid both of the above potential conflicts and maintain completely separate work environments. In most cases this will not be necessary, but it is an option if you need it.
To run multiple instances of RealTest from its desktop icon, simply double-click on the icon multiple times.
To run multiple instances of RealTest from its task bar icon, right-click on the task bar icon and select RealTest from the popup menu.
This starts a new instance, whereas clicking on the taskbar icon just brings the current one to the front (or pushes it to the back if it's already in front).
Another way to start new instances is to open a command prompt, navigate to the RealTest folder (e.g. "cd c:\RealTest"), then type "RealTest" and hit enter.