I believe it is a Mozilla / Firefox problem. I had Windows 7 on my other laptop (in the other room) and it installed and ran without a problem. It will not run after downloading on this new Windows 7 PC (6 GB RAM, i7 Intel chip) and I am signed in as Administrator. I also run Norton 2011 AV.

I've also been in the computer field for quite a while, I don't recall this being a problem in the past.

Another person had suggested disabling the antivirus (AV) scanner to test it out and see if Mozilla will run. Don't do that - at this point in time, all AV software are mature and will recognize Mozilla/Firefox and will not prevent Firefox from running. If there is a bug in all the AV software out there, that is a problem, but I doubt it if there are multiple AV vendors having the same related problem.

  It is a different story if there is an unknown virus/trojan/worm out there creating havoc and the AV vendors are not aware of it.

If it is a PC problem with Windows, then maybe Microsoft is not aware of it but I doubt it in this case.

It seems to be a Mozilla problem. I have tried the latest versions (3.6.13 and 4 beta) without success.

Interesting. I tried one more time - instead of saving it to my hard drive, I ran it directly off the Mozilla site and it installed....

Something is definitely wrong with the Mozilla "save as" process....