Three things you could try:
a) Click Start - Control Panel - Add or Remove Programs ans see if it's still listed. If so, try to uninstall.
b) Try running CCleaner click here and click on the 'Issues' icon and Analyse/Scan for (Registry) Issues. This doesn't seem to do a particularly thorough job but in my experience, at this level fairly superficial level, it very often does the trick.
c) Use System Restore, going back to the point before you first installed Omnipage12. If that does the trick, don't forget to re-check with your anti-virus/ant-spyware progs to bring the signature files (back) up to date.
If System Restore doesn't do it, you might need to use a more thorough registry cleaner such as Registry Easy. But that costs money so maybe someone else can recommend a freebie alternative. But HTH.