wrong "side by side" configuration

Hello. Recently, when I try to start an application, I receive an error, that I would translate from french something alike (in this case for Opera broswer, but everything else bugs):
"C:\Program Files (x86)\Opera\opera.exe
The application couldn't start because it's side by side configuration is wrong. For more informations, please see the application event's log or use the comand line tool sxstrace.exe"

French verion (if a French speaking translator is around, please correct my translation):
"C:\Program Files (x86)\Opera\opera.exe
L'application n'a pas pu démarrer car sa configutation côte à côte est incorrecte. Pour plus d'information, consultez le journal d'évènements d'applications ou utilisez l'outil en ligne de commande sxstrace.exe."

I tried to use sxstrace.exe with cmd, but it tried to explain me how to use it, and I didn't go further. I saw other forums about, but their problems seemed different: it happened after the installation of a game and only this game didn't worked, but as far as I'm concerned, all non windows applications fails at start, like Firefox or Antivira, and even Windows media Player or MSN. That's strange. On those forums, they also said that you should re-install microsoft's visual C++ 2005 (or for me 2010, I'm running seven 64 bits). I downloaded them (visual 2010 x86 and x64) with IE7 and tried to launch the setup, but I had the same error. So I get nowhere since a few days in spite of my tries. I even tried to launch a backup to a previous windows state ("backup tool") but it falled cause my backup seemed to have problems. So I'm very embarassed, I can't use my computer.

Please help me :)
Thank you in advance and sorry for my poor English skills.

Thanks for your reply.
Unfortunately, I've already tried that, but it told me that my backup image was damaged or corrupted, so he couldn't help me. I only see two ways: either I solve this problem with you, or i "format" my partition, I simply delete it, and re-install windows... I've got the CD, but will I get the license? Do I have the right to re-install windows with the same cd?

Thant you in advance for your awnsers :)

Thank you for your reply.
I bought Windows Seven with my components (it's a self-build computer, I assembled the components) on a Parisian shop. I payed it 90€ and everything seemed normal, I could do updates, etc, so the licence is ok and the CD too. I bought an OEM CD. So won't have problems. Have an idea about the wrong side-by-side configuration?*

Thank you in advance for your awnsers :)