I recently started using an old Acer Aspire M3802 and am having problems. Everything was fine until I updated it to Windows 8. Upon my first reboot I was told the CMOS Checksum was bad, and, was prompted to continue or to run a setup, both of which I need to hit a button on my keyboard to perform, however, my keyboard does not work upon startup (I think because USB Legacy Support isn't enabled), however i can not enter the BIOS without using my keyboard, and cannot successfully boot up my computer without inputting a keystroke. I replaced the CMOS Battery but I have to set the CMOS Date/Time, which again requires using a keyboard. I TRIED using a WS/2 to USB adapter and a different keyboard but neither work, is there anything I can do?the adapter should have worked, so maybe try another adapter.also, if you PLUG something into a PS2 port, it only gets detected during boot up, so reboot after connecting something into the purple or green ports.

ideally, a native PS2 keyboard PLUGGED into the purple port on the back of the case should do the trick so YUOU may need to hunt down one of those to get into BIOS to change the legacy USB settings.
have you tried a different USB keyboard and another USB port?
Checksum errors mean the HDD aint talkin to the PC...for whatever reason///i suspect the HDD is failing.
Do you have the manuals?
https://www.acer.com/ac/en/ID/content/support-product/1776;-;
Now about the keyboard. Do this:
Remove the hard drive. (Or just remove the power and data connectors.)
Remove all USB devices except the keyboard. Turn power on. The keyboard lights should flash. If not, poser down and try again. Try another USB port. When you get into the BIOS, reset defaults. Don't worry much about the date and time. The other stuff is more important.

Once you have BIOS set and the keyboard works, power down and put the hard drive back where it belongs. Don't expect the system to work, yum will get an emperor message. The message will confirm that the drive is there, but not bookable.

You may need to do a repair the OS.You will need the CD or DVD used to install the operating system. Set BIOS to boot from the CD or DVD. Select repair system.

Does this hep any?

EDIT: Do you have the Windows 8 DVD? The product key? With it you can get an ISO from Microsoft.
https://www.microsoft.com/en-us/software-download/windows8ISO
After you replaced the the CMOS battery did you unplug the power to the power supply . The reason to do this is the cmos battery is only used when the power supply is disconnected from the mains, like when the computer is in transit.

Having the Date set is important for a windows computer to boot !

When you replaced the cmos battery did everything look ok on the motherboard, No bulging capacitors or a build up of dust ?

Do the Keyboard lights flash when you turn the power on. ? if not leaving the computer unplugged for 10 minutes may reset the fuse for the USB ports and get the usb ports working.
If they are still not working then perhaps try another power supply.

It is unlikely this is caused by a faulty hard drive as was suggested.


I unplugged the PC while I was replacing the CMOS Battery. Just checked the motherboard and couldn't spot any bulged capacitors or large amounts of dust. Both keyboards I used lit up when plugged into the USB port and while using a PS/2 adapter. I tried unplugging the hard drive but the problem persisted. Quote from: man2973 on May 19, 2018, 03:55:38 PM

... I tried unplugging the hard drive but the problem persisted.