USB devices not detected at startup

Hello,

I have a Belkin wireless mouse and keyboard that I use on the computer
that is running Vista. It doesn't get detected upon start-up. Same goes for
a Dell USB keyboard and mouse. I have found that an old PS/2 mouse and
keyboard work fine upon startup, and Vista will detect and install for the
USB devices after I put the keyboard to sleep and wake it back up 1 or 2
times.
Any thoughts on how I might get Vista to detect these upon startup, so I
don't have to use the PS/2 ones? It's rather cumbersome given that the
computer is hooked up to the TV, I'd much rather be able to use the computer
from the couch right from the get-go.
Thanks