In case you don't know someone's found a clever way of running IE 5, 5.5 and 6 on one box. A wee article about it is here:
or you can just grab the files you need here (probably won't be up for long I reckon):
All appears to work well enough, although I've certainly not tested them very much. Unfortunately it seems at least one valid box model hack fails as the browser still thinks it's IE 6. Still beats running through to the other room to use the old computer every 5 minutes.
Why didn't anyone (Microsoft!) release this sooner?