Virtual PC 2004 is meanwhile one of my favorite programs. Currently I test a lot of stuff with XP SP2 and latterly also Linux to showcase interop scenarios. One bad thing is that currently there are no Virtual PC Additions for Linux. 800 x 600 is the standard resolution under Virtual PC 2004 for a Linux system. Currently I've received a nice tip from one of my buddies to modify the XF86Config file manually.

I edited the monitor, device and screen section. The following extract of my XF86Config is working fine in my environment

Section "Monitor"
  Identifier   "Monitor0"
  VendorName   "Monitor Vendor"
  ModelName    "Generic Laptop Display Panel 1400x1050"
  HorizSync    31.5 - 90.0
  VertRefresh  59.0 - 75.0
  Option     "dpms"
EndSection

Section "Device"
  Identifier  "Videocard0"
  Driver      "vesa"
  VendorName  "Videocard vendor"
  BoardName   "VESA driver (generic)"
  VideoRam    8192
EndSection

Section "Screen"
  Identifier "Screen0"
  Device     "Videocard0"
  Monitor    "Monitor0"
  DefaultDepth     16
  SubSection "Display"
    Depth     16
    Modes    "1400x1050" "1280x1024" "1280x960" "1152x864" "1024x768" "800x600" "640x480"
  EndSubSection
EndSection

Now I have nice 1400x1050 which makes me happy