Yes, connect monitor 1 to computer 1 and run the slideshow on it. Connect
monitor 2 to computer 2 and use it for other applications. There is no
other chance, because PowerPoint needs your whole computer, you cant
continue working in other applications on the same computer.
Look at OfficeOne PowerShow at http://officeone.mvps.org/powershow/powershow.html. Among other things, it
allows you to run a slide show on a monitor while you continue to work on
something else on other monitors.