Compaq Presario 5333CL (vintage 2002) XP SP3

Tapping F10 has always been the key to get me into BIOS Setup. The post screen agrees it's F10.

Tried it today to check boot sequence, and it doesn't work anymore.

Don't think the keyboard is bad because holding down the F10 key prevents the PC from booting to Windows, so the F10 key seems to be functioning.

Tried unplugging my new wireless USB mouse and using original Compaq mouse PS/2 mouse, but no change. Keyboard is original USB that came with PC.

Tried a generic PS/2 Keyboard... no luck.

Something has changed.

Help!! Thanks...