Help with videos and Power Shot A560

I have a Canon Power Shot A560. Had all the software loaded on my computer. All was fine for 5 years.

Two weeks ago, I messed things up. Not sure how, but in the end, something called HP PhotoPremier was installed on my computer. AND NOW MY VIDS DON'T WORK.

I can upload my videos to youtube and watch them there. But I can't watch them on my computer, and I can't edit to do things like pick up a still shot from one frame. All things I have done, no problems, for 5 years.

I have done a right-click on the movie, and gone to OPEN WITH. There is this list of options:
Real Player (won't work)
Windows Media Player (won't work)
Quick Time Player (that DOES work, so now I can watch the movie I took on my computer)
HP Photosmart Premier (that is what has caused this mess)
Firefox
CHOOSE PROGRAM

Last one gives me a new pop up menu.

What am I "supposed" to open them with? I have never paid attention - it worked, and now it doesn't.

In that CHOOSE PROGRAM option, I don't see a Canon file, or ZoomBrowser or EOS.

When I open ZoomBrowser EX, and I click on a movie I took with the camera, it used to play from there. Now, it says:
Corrupted Movie/Sound File

But it isn't corrupted, it works on Quick Time and on youtube.

I still have the original disc which came w/ the camera. Should I just load that again? And if I do, will I lose the 3 years' worth of photos I have stored on my computer???

Please help if you can. Thank you.

Reload it, and it should have no effect on photos stored on your computer. I would suggest though, that if you have photos on your computer you don't want to lose, copy them to discs. Then you have a backup set in case of computer problems.
And concerning your movies, run them through movie maker (on most newer computers, or download from the net) and condense those gigantic files down to managable file sizes with no noticeable loss of quality. (Mind you, I'm not a pro at this, but have used it a few times and it worked for me.)