To prevent the MS Tablet PC Ink Pen components to start up, I just unregistered them.

I created an XP batch file like this:

rem -- UnRegister MS XP Tablet PC Ink Pen components
set sys32=%SystemRoot%\System32
set pfcfink=%CommonProgramFiles%\Microsoft Shared\INK
"%sys32%\WispTis.exe" /unregserver
"%sys32%\regsvr32.exe" /u "%sys32%\inked.dll"
"%sys32%\regsvr32.exe" /u "%pfcfink%/inkobj.dll"
"%sys32%\regsvr32.exe" /u "%pfcfink%/inkdiv.dll"
"%sys32%\regsvr32.exe" /u "%pfcfink%/tpcps.dll"
set pfcfink=
set sys32=
pause

In my PC, the components were installed by the MS Visio 2003 Viewer. That program uses an MS Installer Database (MSI), so whenever I would "Repair" such an Office program, the Tablet components get reregistered again.