Hi,
I made a little game with directX, which uses doublebuffering.
The buffers are flipped with DirectDrawSurface->Flip after
a DirectDraw->WaitForVerticalBlank. (Good old AMIGA method :P )
This works fine with Win95/98/NT but doesnt work with Win2k.
The two buffers flicker heavily and it seems that DirectX doesnt wait for vertical blank.
What GFX/Drivers are you using? Some can disable "Wait on V-Blank", otherwise the GF2 would never get above 85 FPS (or whatever your monitors refresh rate is) for instance.
I use Win2K at work (ie now), and the DX stuff I run hasn't shown a (noticeable) flicker.
Mirno