Windows 10 uses a different driver model that may or may not be compatible with older versions. That's all it comes down to. Rather than messing around in AE you need to install a legacy audio driver/ enable compatibility mode settings, if possible. Otherwise you may have to live with this limitation or need to upgrade.
...and you may may find even more incompatibilities in the future. Your version of AE came out about seven years BEFORE your operating system did. There's no guarantee everything will work as it did under Win7.
Thanks for the replies. I guess it's time for me to upgrade my software or learn some new one. As far as drivers are concerned, have not found any legacy ones that would work. I am still on the lookout though .