Now when I have Platinum installed and working OK, is it safe to uninstall X3, without risking to loose any essential components, synths etc in the process?
 
/Hasse G

The standard answer is remove old versions before installing new ones. Because all versions of SONAR share components, there is a chance, uninstalling X3 will remove some shared utilities. Removing a previous version of SONAR frees up less than 200MB. If uninstalling X3 does cause loss of function, the fix is uninstalling/reinstalling the Platinum core.

OK, thanks. I'll think about about what to do. Do you get any options during uninstall?

I don't think so but I have not bothered to uninstall a version of SONAR on any machine.  My current machine has X1 through X3 Producer and Platinum.

As said, there's no reason to uninstall the old versions. They certainly take up no room and you never know if you might need it again. Delete the desktop icon and forget about it. 

Don't forget you also have to clean out all traces of Sonar and it's plugin folder in the registry before you do a clean install of a new version. If you don't you can run in to some real problems with earlier installed versions of DimPro, etc. You have nothing to lose by keeping the old versions on your system.

I would just delete the shortcut to the program and pretend it wasn't there.  I just spent an evening or two hunting for old softsynths that were missing on my DAW because I didn't bother to install old versions of SONAR X series when Jim at StudioCat built my new one.  I wouldn't want to possibly have to do that again because I deleted an old version.  You might not notice it for a couple of years until you wanted to open an old project.

Thanks all, for good advise. I'll just bury X3 on C:/ then. :-).