I installed X1 essentials on my custom DAW which runs XP PRO SP3. I had to use another computer to get SP3 since the disk came with SP2 and the DAW is totally off line.
I got SP3 installed and the installation of X1 went perfectly. No problems.
I do believe what I did though to install it, was to run it as administrator. Right click the icon and select RUN AS.... then select Administrator.
There are a few things that install correctly when they are run as administrator. And cake products do fall into this category.