Assuming you did a full install of Paint Shop Pro 8, you'll need to modify it to uninstall the Virtual Painter 3 demo filters prior to installing the full version of Virtual Painter.
1. Click Start > Control Panel > Add or Remove Programs.

2. From the list of currently installed programs, choose Jasc Paint Shop Pro 8, and then click Change. This starts up the InstallShield Wizard for Program Maintenance.

3. Click Next.

4. Click Modify, and then click Next.
5. Click the Virtual Painter Filters icon (not the text itself, but the icon). You'll see these options appear. Click the bottom option, "This feature will not be available.", as indicated in the graphic above, and then click Next.
6. Click Install. (Note that although the button is labeled "Install", you'll actually be removing the Virtual Painter demo filters from your Paint Shop Pro setup.) You'll then see an InstallShield Wizard progress screen.
7. Click Finish when the wizard is completed.
When you restart Paint Shop Pro 8, the Virtual Painter demo filters will be removed from the Effects menu. At this point, you're ready to install the full version of the Virtual Painter