Need to change my log on settings(Previous user never gave me his password)

[Viktor Largo]

Ive just purchased a used ibm thinkpad with windows xp
home pre-installed, there is a log on before windows
loads, that lets you select limited or full accessibility
to changing and installing programs and settings inside
the OS.

Im not used to XP at all so dont understand the use for
this function.

I need to know if its possible to change the primary
administrator account, i can access the computer from a
limited account user.

please help me.>>>