More input needed, drivers, etc.
Cubase VST runs fine on XP.
Do you have a Athlon system with VIA chipset?
Install the latest 4in1 driver.
Get the latest soundcard drivers.
Get the latest videocard drivers, they can crash Cubase too.
Get the latest Cubase update from
ftp://ftp.steinberg.net/download/pc/Cubase_VST/
and/or get the latest dongle drivers (POS1055).
What FX are installed? Some versions can cause crashes.