Ummm...
Have a peek in C
Windows (using Knoppix) to see if you can see the archive of the files replaced in the last update - or an earlier one.
I think it "hides" them, but I suspect Knoppix would ignore the "hidden" flag.
You may then be able to copy the relevant files back to their home locations, thereby overwriting the "new" ones from the update.
In Win XP, they would have names like $SPuninstxxyyzz. Inside there, you may find something called spuninst.exe (won't run under Knoppix), or you may find a load of files (which you can copy around).
My XP installation got very cluttered with these, till I decided I wasn't going to roll back that far, and deleted all but the last couple.
Don't know if Vista does things the same way. I'm pretty sure the Win 7 RC doesn't.