greetings from germany

First of all, I used Spybot for over a year and always without any problems. But since about 1 month it does not start anymore and I'm close to reinstall Windows XP, just to make sure it's not the fault of a change, caused by a programm like tune up utilities registry cleaner or whatever.

What I did so far:
I completely reinstalled Spybot S&D, removed the last existing folders of it and cleaned everything in my registry, what was not removed by an uninstalling. I rebootet several times after uninstalling, clearing registry and so on. Still, after installing Spybot and I try to run the .exe, absolutely nothing happens. Though updating works without any problem, the main programm does not start. But though it does not start, I can see the progress running by opening the Windows task manager. If I run it two times, it appears twice as an active progress, with the same details as the first got (same CPU usage, which is actually 00, and the the same memory usage, about 2.900K).

Can anyone help me out?

I apologize for every mistake that I eventually made, I tried my best :D