This is a modified version from the patch used by Mandrake to turn
the screen blue at startup. Of course I chose to make it black.

--- xc/programs/Xserver/dix/window.c.orig	2002-12-26 11:36:41.000000000 +0100
+++ xc/programs/Xserver/dix/window.c	2002-12-26 17:26:05.000000000 +0100
@@ -307,6 +307,7 @@
     WindowPtr pWin;
 #endif
 {
+#if 0
     ScreenPtr pScreen = pWin->drawable.pScreen;
     GCPtr pGC;
     unsigned char back[128];
@@ -348,6 +349,21 @@
 
    FreeScratchGC(pGC);
 
+#else
+   {
+     /* Mandrake Linux specific: set our background color */
+     unsigned short 	red = 0x00 << 8, green = 0x00 << 8, blue = 0x00 << 8;
+     Pixel		pixel;
+     
+     AllocColor((ColormapPtr)SecurityLookupIDByType(wClient(pWin), pWin->optional->colormap,
+					      RT_COLORMAP, SecurityWriteAccess),
+		&red, &green, &blue, &pixel, wClient(pWin)->index);
+     ChangeWindowAttributes(pWin, CWBackPixel, &pixel, wClient(pWin));
+     (*pWin->drawable.pScreen->ClearToBackground)(pWin, 0, 0, 0, 0, 0);
+     
+     /* ErrorF("xf86CreateRootWindow() put background color %d\n", pixel); */
+   }
+#endif
 }
 
 WindowPtr