no sample runs on my 8400 GS: initialization error


I have an nVidia GeForce 8400 GS on a WinXP system.
I tried to run any sample (from the CUDA samples browser), like e.g. MatrixMultiplication, SimpleOpenGL etc. But always I get an error (‘error initializing device’). My 8400 GS is working, my monitor is connected to it and I didn’t have problems with ‘normal’ WIndows working. But the CUDA samples all fail.

I opened the ‘files’ (source code) and saw that the very first line in MatrixMult fails - where the device is initialized.
I get an ‘unknown error’.

What’s wrong?

Thank you!!!

PS: I searched this forum for ‘unknown error initialization’ and got 33 pages of topics, sorry, I can’t find an answer to this question.