try this ling of a search i just did in googles - maybe it may give u a clue
I have a gateway laptop running win98. After startup I immediately get this RUNDLL32 error message. When I close that box it is immediately followed by another error box stating: "EXPLORER caused an invalid page fault in module MZSYSTEM.DLL".
I have SpyBot Search and Destroy, Ad-Aware and Norton AntiVirus software on my machine.