Invalid page fault at mfc42.dll

When I double click My computer, IE, control panel, and nearly every other shortcut to a program on my WIN98SE pc I get “Explorer has caused an invalid page fault at mfc42.dll.” Then The PC dislays “Internet explorer will now close” I am working on this PC for a friend who has chosen not to install a virus program. The PC is acting like it has the pretty park virus but I would like to know if anyone has another idea. Thank you!