Can I install a second MT4 trading platform to my PC? How can I do that?

Yes you can, by installing it to a different location.

After following the first 4 steps from “How to install the MT4/MT5 on a Windows PC”, continue with the steps below:

Instead of ‘Next’ click on ‘Settings’.
Click ‘Browse’ and select a different/new folder to save your platform and click ‘OK’.
It is recommended that you change the name of your folder from the ‘Program Group’ field.
Click ‘Next’ to finalize the installation.

Please be aware of that MT4 trading platform is a RAM consuming software. Thus, running many trading platforms at the same time can delay the processing speed of your PC and can directly affect the execution speed of your trades.