If you have downloaded Open Office version 2.4 to your hard drive and then
attempted the install from there, do you get the same error? It isn't
totally clear what you are trying to do but: If you attempted to run the
install from the download page, that is probably your issue.
Download Open Office 2.4 from
http://www.openoffice.org/ to your hard drive.
Go to the download location on the hard drive and click on the program and
follow the prompts to install.
Microsoft's Office program doesn't need any update to install Open Office as
they are totally separate programs, install to different hard drive
locations and I have never had a conflict between the two sets of programs
as I have MS Office versions 4.3, 97, 2000, 2002, 2003 & 2007 and Open
Office 2.4 installed on the laptop that I am using to write this post.
Have you tried to open the Word Perfect 12 document with MS Word? Some
times the program will open the .wpd document and sometimes not. Possibly
have the Word Perfect program save the document to a compatible Word version
document? There is that feature in WP 12.