Peter,

This is a rough answer and someone with polish may be along to provide
more technical details.

You can have 2 or more Office suites on the same PC, but unless you
have something like Virtual PC install which allows for 2 or more
operating systems then you can only run one suite at a time. If you
use 1 and then want to change to the other there is a significant delay
as the registry updates from one suite to the other.