Explorer – program has performed an ill

I found a computer. It has Windows 98 Plus. When I click on Contraol Panal, I get EXPLORER caused an invalid page fault in module KERNEL32.DLL at 015f:bff9dba7. I deleted .pwl file and restarted but I still get this error. I suspect this system mayhave the worm HAPPY99. What do you think? If so, what do I do, reload w98?