Just tried this on another PC that's got XP Pro loaded and it worked (originally worked on Vista). However, both are 32bit systems and not the 64bit you appear to be running? If so, that's likely the problem. Try manually installing the files to "Program Files" instead of "Program Files (x86)" to see if that makes any difference (I can't remember if Windows does some auto-config when it reads "(x86)" in the file name on 64bit systems). Failing that you're going to need to find a way to run Blender in 32bit mode. I don't know how you'd do that I'm afraid (unless there's a 'properties' setting that can be used - right-click the exe and select "Properties").
