Ok, I found it in the system32 folder and replaced it with the new version. It now seems to work. The mistake I made was to change the installation folder you indicated and create a shortcut towards the extracted file (I use it as a programme as wel as a screensaver)
The shortcut launched the new version, but the old version was still in the system32 folder. I use XP, by the way. (At work, I run it on my mac at home