  Several schemes to introduce finite width effects to reactions involving
unstable elementary particles are given and the differences between them are
investigated. The effects of the different schemes is investigated numerically
for $W$ pair production. In $e^+e^-\to W^+W^-$ we find that the effect of the
non-resonant graphs cannot be neglected for $\sqrt{s}\geq400\GeV$. There is no
difference between the various schemes to add these to the resonant graphs away
from threshold, although some violate gauge invariance. On the other hand, in
the reaction $\gamma\gamma\to W^+W^-$ the effect of the non-resonant graphs is
large everywhere, due to the $t$-channel pole. However, even requiring that the
outgoing lepton is observable ($p_\perp > .02\sqrt{s}$) reduces the
contribution to about 1\%. Again, the scheme dependence is negligible here.
