Problem Installing Certain Things

I tried to install Nero for my dvd writer today, but I get an installer error that says "The executable file has been corrupted".

I also installed Power DVD not too long ago, got some error while installing, but it actually installed. However, when I try to run it, I get the "PowerDVD has encountered a problems and needs to close."

Lastly, I tried to install Warcraft 3 today, but got this error about 40% through installation: http://img.photobucket.com/albums/v333/iaacp/wc3error.jpg
That link comes out uber small, I dont know why, so I'll type it out.

This application has encountered a critical error:

Error #131 (0X85100083)
Program: C:/DOCUME~1/Evan/LOCALS~1/Temp/war3.install.exe
File: D:/setup.mpq
Press OK to terminate the application.

Any idea's why I'm getting all these errors/problems while installing things?

Was this posted in the wrong section? Wasn't sure exactly where it would fit.

Are you installing Nero and PowerDVD from a disc, or from an installation program (.exe, .msi?)

If from a disc, check your optical drive.

If from an .exe/.msi, are you overclocked? Are you certain the system is stable?

From a cd. by optical drive, do you mean the tray or lense?

the cd/dvd drive itself. it might be going bad. do you have a spare?