|Toshiba Satellite L645D (Win7 Home 64-bit) here...|
Upgraded to Win10. Suffered through a couple months of frequent "insufficient memory" errors and video driver changing resolution at will, going black with cursor visible or internal monitor going dark. Ran memtest86; no errors on two passes.
Win10 pushed update, internal monitor went dark, but would drive external monitor. Checked BIOS; no monitor default setting. Memory/vid errors continued, but at one time, video driver enabled both internal and external monitor, so it does not appear to be a hardware failure.
Backed up personal files and took machine to "out of the box" Win7 factory reset. Internal monitor did not come along for the ride.
Upgraded to Win10. Internal monitor still MIA, but vid errors have stopped. Memory errors still occur, but frequency has dropped from every other hour to close to a week since last error.
Still looking for a way to resurrect the laptop's internal monitor. [Fn+F5] monitor switch says I don't have an internal display, just the "CRT" external.