1) Create another Windows XP account to use.
2) Use the shell command RUNAS to run the other instance of PowerPoint under the other account.
Example: having created a special account "xxx", when logged in as "yyy", and already running PowerPoint, use [Start] [Run...] CMD, and then enter a command similar to:
C:\> runas /user:xxx "c:\program files\microsoft office\office11\POWERPNT.EXE"
Pro: you get another instance of PowerPoint.
Con: it's running under the other account, so will save files to the My Documents folder, etc. of that other account. But that could be overcome by changing the MS Office folders locations of where the Dad account saves its files. You need never actually log in to Dad through the front end of Windows XP.
You can make a batch file with a shortcut if you like, so it's as easy as clicking an icon called "Second PowerPoint".
Tools > Options > View > select Window in Taskbar
Window > Arrange All
This will result in showing you both documents in a single PPT window Side by Side.