Just a guess...
Hey Kido
I am really new with XP, and advanced logon options and the like, but I am
sure that if I am wrong, someone will jump in to correct (and I do hope they would).
The only way I would think you could do it would be if you created 2 different installations (a dual XP/XP boot?) - one for the mom unit, and one for you. As I see it, no matter the user, the Base OS is using the same explorer.exe file - what you do, will effect all.
Now one way you "might" be able to pull off a fujiriffic trick, might be to burn
your OS to CD - thereby completely leaving her OS (and the main copy of XP) alone. You would be able to freak your friends out too. Your system should be more then able to boot from CD (might have to change your boot devices and order in the BIOS though - just depend on how it is set up now).
I have NEVER tried this, but it would only take a few minutes to find out, and it can not hurt anything to try, but someone might have info I do not, and save you the effort, if they know it will or will not work...
Imagine you might need "disk at once" capablitiy on the burner though, for write back...
Good Luck...