Older or special Windows XP keyboard Drivers might not be signed. This applies to some versions of \Driver\Ps2, \Driver\Ps2Led, \Driver\qkbfiltr, \Driver\PCTCore, \Driver\hask, and \Driver\HpqKbFiltr. Others are specialty devices for gaming, etc.
Find the driver file in %systemroot%\system32\drivers (usually with a “.sys” suffix. e.g. \Driver\Ps2 = Ps2.sys)
Select the file, right-click, select Properties
Check for “Digital Signatures” tab. If the file is not signed, check with the manufacturer for an updated driver.