I want to install DS4 Pro, without messing up my DS3A. Is that possible? And if so how please?
Just install DS4.5 and your fine. I have DS3A 32bit DS3A 64bit and DS4.5 32bit and DS4.5 64bit all installed without any issues.
Possible? yes, and (for me) it was a smooth install. It sets itself up in a separate folder hierarchy and doesn't conflict. I have DS2/3/4Pro installed, and happily coexisting.
The Problem I've had is PEBKAC (Problem exists between Keybaord and Chair) so that my content directories are all screwed up.... my problem of not really knowing what I was doing at the time, and being a dabbler, rather than really learning the hierarchy of the content.
My main suggestion will be to make sure if you want to "merge" the content directories or keep DS3 and DS4 content libraries separate, and then proceed.
I am still looking for that magic button that will scour all my content directories - DS2/3/4 Poser 4/6/9 - and combine them all into one (or two) convenient locations.
The Method I use/used when I had DS2 installed was to just use my DS3A content folder for all None Genesis content. I set DS2 and DS3A to both use the DS3A content folder in the Prefs. All files showed and worked. I let DS4/DS4.5 create the My Library folder and installed all my Genesis content to it. I then set DS4.5 to include the DS3A content folder in my Prefs. I then also had access to all my content in DS4.5.
EDIT: You should probably keep the Poser only folders seperate but add them as content folders in Prefs as well.