BTW here are some interesting cases where win32k.sys may cause similar memory corruption:
https://support.microsoft.com/en-us/kb/2908190
(win7)
https://support.microsoft.com/en-us/kb/971251
(win2003)
https://support.microsoft.com/en-us/kb/872797
(winXP/2003)
kb2908190 is particularly interesting since it is related to drawing fonts. Alas this is for Win7 and not XP.
I wonder if you have the crash when you copy an image to clipboard? That would confirm you have the issue described in kb872797.