how to fix TWAIN in Win2000

Hi to all experts here:
I need advice on whether TWAIN is fixable in Win-2000-Pro. I installed twoo printers (Lexmark and Canon, both all-in-one, i.e. with scanner and printer). Then decided to uninstall Lexmark - and when I did, I did answer "Yes" to deletion of the potentially shared files. After that the remaining Canon got affected - its scanner part stopped working properly, giving message "cannot find TWAIN". So, it apears, by uninstalling Lex,ark, I did delete TWAIN, affecting Cananon's scanner. I tried to re-install back Lexmark - result remain the same - no scanner portion of it works (neither, Lexmark or Cannon) and for same reason - "cannot find TWAIN". I tried to run TWAIN generic installation (downloading it from the Web) - it did not help, even though *.exe file was running fine for installing the generic TWAIN (for Win-2000).
So, the question is - how to fix the TWAIN in the system? Is there repair procedure for Win-2000, which would reinstall the TWAIN ? I can re-install the whole system, only this route is hard to engae into, because after that I have to re-install all my softwares (Matlab, medias. programming languages - it is too many at the moment, I hasitate to engage into that radical route as I need the computer running non-stop at the moment).
In Win-98 I remember there was way to re-install the system keeping other soft uneffected, which often helped fixing system problems. Is there such way in Win-2000 ?