the wonders of technology Switcher unit
this isnt the exact one i have im still looking for that one but basically 2 pc's plug into the unit then one mouse and keyboard (ps2, sorry aint seen any usb one's) and also plug one monitor in the front and theres 2 leads coming out back... you then use your keyboard to swap between the computers by using the combination " scroll lock, scroll lock, esc."
very useful in my opnion :) hope this helps somewhat.
it is available from the radio spares catalougue (if you live in the uk.) or i think you can order to other contries via this link Linkage