One of my greatest irritants with spell checkers is how they default to US English. I happen to be born and bred in Singapore, a former British colony, so I prefer to spell words properly thank you. ;-)
So it is pretty annoying to be informed over and over again on five different computers of Microsoft Word or PowerPoint that I should not be spelling "organisation" and be hip and go "organization". Sorry, I pronounce or-ger-nye-say-shen not or-ger-nye-zay-shen, yo. But the cool thing is the Microsoft Office dictionary feature allows adding foreign words into the dictionary so it won't think that my spelling $uX0rs. And so in the midst of adding in the correct spellings, I accidentally added a half-written word into the mix.
Oops. How can I rollback that action?
Turns out it ain't too hard to find where these extra words are stored. For a Windows Vista system, the custom dictionary is stored as
C:\Users\{USERNAME}\AppData\Roaming\Microsoft\UProof\CUSTOM.DIC
Open it up and edit it like a regular text file.