Blue screen error at shutdown/restart

Everytime i shutdown/restart my computer (after being on it for a while) I get a blue screen error. Does anybody have any idea why I get a blue screen error whenever I restart or shutdown my computer? this same thing happened about a month ago on mycomputer, and I downloaded a windows shutdown patch but now the error is back, and the patch won’t work anymore. Any ideas would be greatly appreciated. ALso my computer is fairly new and i’m operating on windows 98 SE