I had a similar problem, and it turned out that the CMOS battery was dead. The CMOS battery allows the computer to maintain the BIOS memory, even when the computer is off. If the CMOS battery is dead, the CMOS won't respond to the boot command. I replaced the CMOS battery, I went through a start-up process for the BIOS, (because the BIOS had returned to its default condition,) and all was right with the world. I now keep a record of all BIOS changes. It took me a long time to figure this out, but a recently met a wise man who, changed his CMOS battery each year and had a dual parallel battery rig that let him change the battery, WITHOUT interrupting the electricity to the CMOS, and losing the CMOS settings. In normed use the CMOS battery lasts 1 or 2 years, but can go as long as six years, But when it dies, so does the computer (at least, until it is revived by serious effort). This may not apply this the specific "memory change" case, but, whenever components are changed, that puts stress on the CMOS battery, and that stress might kill an old CMOS battery Gerry Blodgett