My hard drive went bad. I insatalled a new hard drive and had a backup external hard drive for my applications. I had to update to a newer versoin of OS-X, and now my applications won't work.

By newer version do you mean Mavericks OS 10.9? There are quite a few things that won't work with Mavericks.

You may wish to revert to the OS you had before - which I gather was Snow Leopard 10.6.8.

Did you restore the original OS X applications from your backup onto a newer version of OS X? If so, that's why they don't work. You will have to reinstall this new version of OS X.

If you have old PPC versions of applications that worked with Snow Leopard or earlier, but have now installed Lion, Mountain Lion, or Mavericks then you need to replace the PPC versions with upgraded versions that run on Intel processors.

But you need to provide more specific information to go further with this.

All your older PPC applications should continue to work with 10.6.8, provided you have installed Rosetta, which allows them to run under a virtual PPC (Power PC) environment. When you first opened one of those you should have been prompted to do that.

Are you certain it's 10.6.8?

Why don't you list just which applications aren't working.

Jordyosu wrote:

Keynote, Numbers, and Pages

Which versions of those?

Have you run Software Update under the  menu to check for newer versions?