I read on a post on a forum here so I edited my setup.xml like this:

<Property name="AcceptLicense" value="1" />
<Property name="SHOWSERIALDIALOG" value="false" comment="true will show the serial number dialog, false will skip it" />

<Property name="SERIALNUMBER" value="XXXX-XXXX....." persist="1" comment="When you remove the hardcoded serial number, just set the value to blank, do not remove this node or the SERIALNUMBER will not be saved after you perform an admin install" />
<Property name="ALLOW_PRODUCTUPDATES" value="0" persist="1" comment="needs to be saved from admin installs, Script.dll will default it off if we are running an admin setup" />

The I downloaded the service packs 1 and 2 (don't know if 2 includes 1).  I extracted each using Uniextract and then applied over my source directory using command: setup.exe /admin (this prompts you for the source directory).  I think you can just run PSPX4_SP1.exe /admin and PSPX4_SP2.exe /admin and it will do the same thing.

You can then install from your source folder silently with command: setup.exe /PASSIVE /ALLUSERS=1 /QN

The silent uninstall works in a similar way in that you must run from the source folder: setup.exe /X /Q

There is a registry entry for uninstall of: MsiExec.exe /x{00AE1A2D-7BC2-4359-A0EC-E19F36E391BB} BUT I found this DOESN'T WORK silently even with /QN

For uninstalling Corel Paintshop Pro X4 silent you can use the following commandline:

C:\Program files (x86)\Corel\Corel PaintShop Pro X4\Setup\{00580795-581C-4587-B9F2-3720D7AB37F}\Setup.exe REMOVE=ALL REMOVEUSEFILES=1 /QB-