Problems loading windows 98SE

When I load 98SE and drivers to a particular machine it starts giving me registry errors. Hard drive is good. It also does not load everything in device manager. When I swap out memory it works fine and no errors, but still does load certain driversin device manager. Machine originally had windows ME on it. If I load ME on it everything loads fine, but customer does not want Millenium on it. In a bind is there anything I can do or is this just one of those machines that were made for ME and not able to load 98 SE without problems? At the point of telling customer she is just going to have to live with Milleniun.