Best not to just delete but to use the progs uninstaller.
Then look in your C drive for the left overs and delete them.
Is firefox or opera part of your startup group?
I had a problem with my browser Firefox so downloaded and installed Opera. When Firefox got back to normal I went back to it but could not make it the default again, and had to delete Opera. After this when I boot up the message The Parameter is incorrect comes up every time. I click OK and message goes away, but now attachments do not come through on emails