i just upgraded from the free version of Synthesizer 5 to the Pro Studio version. Do i need to uninstall the free version before installing the Pro version?
You can directly install the pro version.
However, if you plan to uninstall the basic version, you’d better uninstall the basic version first and then install the pro version.
「いいね！」 1
I just did the opposite before reading your message.
What problems can I get now?
Okay, I got it.
The program didn’t work properly as a VSTi anymore.
The Host DAW crashed and a lot of other problems. (no voice sound etc.)
Solution : I did another installation, the installer didn’t ask the serial number again (because same PC), so no activation is lost and all works well again. 
「いいね！」 1
As long as you install both versions in different locations such as programs 64 / syhtn v old ( an install the free version there ) than install the pro version. You should be able to install the free and pro versions on your computer.
Couldnt the guy go to program 64x create a new folder an name it like synth v free and install the free version there. Than install the pro version like you would an keep both installers ?
Independent of where the program is installed, the user data is shared among all versions of Synthesizer V Studio.
「いいね！」 1