A search for charged massive stable particles has been performed with the D\O~detector at the Fermilab Tevatron. The signature is two particles reconstructed as muons, but with speed and invariant mass inconsistent with beam-produced muons. No excess of events is observed and limits are set on the production cross-section for pair-produced stable stau sleptons based on $390$ pb$^{-1}$ of data. Limits vary from 0.06 pb to 0.62 pb, depending on the stau mass, and are the strictest Tevatron limits to date. Mass limits are also set for stable charginos. The limits are 140 GeV for a higgsino-like chargino and 174 GeV for a gaugino-like chargino. These are currently the best limits to date for stable charginos. (Conference Note)