Before I abandoned the Windows world, I configured a few of my own keyboard layouts, so I could more easily type in the characters I wanted in the various languages I use. The standard keyboard layouts for some of these languages would have required too much relearning. Microsoft has a keyboard layout utility available for free download.

As for the oe ligatures, I don't think they're included in the Windows basic codepage or the Latin-1 charset. That may explain why Windows doesn't handle them more nicely.

As for the Mudcat "odd encoding treatment", read this thread:
Entering special characters