XP dpi scaling grayed out: From Microsoft Tech Support.

 

We can turn on this option by editing the following registry key:

First: we should make a backup of your registry just in case.
  • Click Start, type REGEDIT in the Start Search bar and press Enter.
  • Select Computer (the root node) in the left pane,
  • click Export under the File menu,
  • choose All under Export range,
  • Select Desktop in the Save in box and type backup in File Name, then click Save.

Please Note: The backup file is on the Desktop and named backup.reg. We can simply restore the registry by double-clicking the backup.reg file.

 

Next: to edit the key we need do this.

  • Click Start, type REGEDIT in the Start Search bar and press Enter.
  • In the left pane, browse to [HKEY_LOCAL_MACHINE > SOFTWARE > Microsoft > Windows > DWM] by double-clicking each directory in turn.
  • In the right panel, double click UseDPIScaling, set the value to 1.
    • If there's no UseDPIScaling value, please manually add it.
      Right click and choose New->DWORD(32-Bit) Value.
  • Close regedit and restart the computer.