It should be under C:\Program Files

If you look for Omnipage or perhaps Nuance you should find it. There might be an uninstall programme in the folder. if not just delete the folder (as long as you are 100% sure you've got the right one)

Then you might wanna run registry mechanic or similar to get rid of the unwanted registry entries. (Never understood the need for a central registry myself - much prefer the unix way of doing it with individual config files)

Disclaimer - If you f*ck it up - it's not my fault