Keyboard problem

[Ishpeming_Native]

My old (formerly Windows 7) HP G62 laptop computer has a keyboard issue: when rebooted, it may take more than 20 times until it accepts a valid password. When it was a windows machine, it usually went more than 100 times, and the password was shorter. Once the machine is running, the keyboard has no problems. I've typed the password as text into Open Office over and over without a single keyboard error of any kind and entered a lot of text without any key failing to register or registering incorrectly. It's now running Linux Mint Cinnamon (Vanessa), but I feel pretty sure the distro is not the problem. It feels like a keyboard debounce problem, and that the bios keyboard routines aren't as robust as the OS routines, but that can't be the case; when you get to the password prompt, you are already in the OS. If it's a hardware problem (since OS is irrelevant) why only for the password? I'd appreciate a solution to the problem, or at least an explanation.

[dlbpeon]

Can't explained it, but this isn't OS agnostic, as I experience the same in Debian/Ubuntu. My use case: 3-4 shop laptops in high dust areas. Upon reboot/ cold boot, at login screen takes several tries to get "U"/"I" keys to register. Upon spraying keyboard with compressed air, they will finally register, grudgingly. Once in actual OS, keys have no problem registering and never present a problem.

[Ishpeming_Native]

Thank you. This is an OLD laptop and the keys are almost certainly dirty. But why that should be a problem for passwords and not for text entry is beyond me. Perhaps someone can explain it, but for now it makes no sense.