I get paid to be called stupid.
I just tried installing the 4.5 platform, and stupidly I didn't change the default destination directory, 'SFP4'. It overwrote the SFP4 directory, the platform actually launched after that but after trying to install some plugins, the platform stopped working completely.
Fortunately I had a ghost (backup) of the drive, so now I'm back at square 1 again. Tomorrow I'll try installing. Should I install it to 'SFP4.5' folder now, and keep copies of both SFP4 and SFP4.5? Is it possible/advisable to have both on your computer (this way I can migrate over with a bit of grace period).
In the course of all this fun, I found that I couldn't delete the SFP4 directory (using Windows Explorer) even when the Scope platform was not running, some files were still locked. I don't see any way to delete SFP4 using the Control Panel, can I just delete it using Windows Explorer after I've switched to 4.5?