Shutdown problem – Any ideas?

My Win 98 has started misbehaving (again)

Serial no. C772100537
Model Packard Bell Pulsar C400/S

Windows says it is shutting down but then will either hang on that window or go to a black screen covered with lines of dots and a cursor that won’t move. After shutting off via the button on box when re-boot sometimes it boots up okay and others it will run a scandisk. The crash is not consistent (it doesn’t happen every time – just enough to make it a complete nuisance). Troubleshooting says everything is running fine.

Any suggestions?

Linda Sawicki