For the time being i'va found a temporary solution.
Got rid of the new TwinMos 512MB RAM-modules and put in the old 256 MB moulde i know works perfectly.
Then i used a Aopen 300 W PSU and i actually managed to insatll driverset NVidida 27.20 from a clean install.
So i think t probebly was the PSU , but the 300 W i have now doesn't deliever more than 10 W more, on the sheeth, but being more "Quality" an wieghing a whole lot more than my Elite 300 W i guess the AOpen produces at least 30+ W under load.
All though i still gonna check the 512MB Modeules one by one, and i'm gonna buy a more powerfull, 400-500 W Powersupply soon i at least has got the darn vard to install propery without blackscreens.
The more powerfull powersupply is to make shure that i have enough power when playing games mounting case-fans etc.