Quoting: art b
do i need a copy of the o/s to reset the machine...
Yes, but I don't really know that much about PBs running Tiger.
Usually it is something like hold down C at start with disk in to launch darwin installer.
Most people format the system to ensure they haven't left anything on there, then re-install from the disk the OS - it takes like an hour on a *real* mac, unlike a PC install of Windows that can take days
If she is the admin account, can you just setup another account and use that as 'yours'?
^ All this assuming Tiger and PBs have the same infrastructure as Leopard
If it affects how you can use the machine, ask for your money back as she is in the wrong.
Note - I doubt you could install Leopard on that machine without slowing it down loads - check specs, if it will run Snow Leopard you could buy it and install instead.