Network Wizard not loading

I have a problem with a numbre of XP programs not loading properly. If I try to use Network wizard – I get to the 2nd screen and the program disappears! Same thing happens with other XP programs – eg if I try to add or remove programs – I get into selection area and suddenly the screen disappears and I am back where I started. No error messages. Memory 512KB, over 60% free, ditto CPU – Even small programs like trying to add exceptions to Firewall – I start working and the screen disappears after a few seconds.
Any suggestions….?
Regards Alex