At firts: a big sorry for my bad english....

I've been since one week Satelco DVB-S USB box. On my normal computer, the BOX with Sceneo AbsolutTV works properly.
Yesterday I connected the box with my laptop connected and installed ProgDVB.
After a few problems I have successfully connected with Astra 19.The Channelsearch works and found many (ARD, ZDF, RTL, Sat1, etc.).
Unfortunately, I can't see a real picture. ProgDVB makes the picture only in the upper quarter . Sometimes it is to the half, but then goes back to the first cm. That is what happens all the time (relatively fast). The sound stutters the whole time.
I connected the box then back to my other computer - no problems, great picture.
Can someone help me?
The notebook has the following facilities:
Dell Latitude D531
AMD Turion X2 TL60
2GB Ram
Vista Ultimate
Greeting Michael
P.S. Mpeg2 videos can be played without any problems (with ProgDVB)
I've also installed the Cyberlink PowerDVD (because the codec)