I've been using the Tredosoft's multi-install. Did you try that version instead of the standalone 6?
I have now, and it works!
So the working methodology seems to be:
- Upgrade the regular IE7 install to IE8.
- Install IE7 Standalone to get IE7 working
- Use Multiple IE to get IE6 (and other older versions of IE if you so desire).
IE6 throws up a couple of errors about DLLs something-or-other but does seem to run just fine.