Windows system error “BOING!”

OS: WIN98SE/350mhz/256RAM: recently installed WIN98SE and e’er since, when I’m loading software or running apps, my computer goes “BOING!” — literally — and crashes or at least interrupts my downloads/installs/apps. Thought it might be display related: nVidia Vanta, but checked HD and even reformatted HD and reloaded all, but problem still recurs. Have never experienced this under previous OS: WIN98 w/same apps and hardware, so am wondering. Thought it might be Zone Alarm, but for the life of me can’t TS this problem. Any ideas not involving violence?

THX/GJB_