Try accessing the bios and see ifyou can use the keybaord there. Of course if it dosn't let you access the BIOS not much you can do. Did this happen right after instaling win10 or did it work for a while then quit working?
If it has not worked since you installed win10 could be a driver issue if you used win10 from microsoft instead of from PC provider.
Bios is usually accessed by pressing akey during the boot up, like delet, F2 or some other sequence. Sometime on boot it will tell you waht key to use.