ok!
my monitor is NeC MultiSinc XV17 (too old..I know:o )
Windows recognized my monitor as it is( Windows has two options that I tried Xv17 and Xv17+)
When I had 6.31 detonators installed I had no problem I Could go in 1280x1024x32 resolution. With 6.50 and 7.97 ( I think starting from 6.50 ) 1280x1024 resolution disappered from my config options.
Then my (old:o ) monitor supports this resolution , windows knows my monitor..then the prob is the driver... then I'm....
ciao thymios