Is very old now. But it does get its 1st of the month canned air cleaning since new. There's that and the banged up OS issue. That is, many keyboard mouse issues can be a sign that some keyboard logger snuck in. Test that by restoring it to factory condition when you are ready.

The age of this isn't helping here. It could be hardware issues. At least you know the 1st of the month routine is or is not being done.
Bob