Downloaded Files Blocked

For awhile now my files that I D/L are all blocked and will not open. I can go to file properties and unblock them and then all is good. But I obviously messed something up somewhere to have this change. I just don't know where to look, to put it back to normal. I have rechecked my virus software and internet settings. I'm sure this is a security setting someplace but not sure where. I'm at a loss and need help.

Running:
Win7 (32bit)
Firefox

 

Ok I gave this a shot and it didn't pan out. I know it must be a setting I accidentally changed, I just wish I knew what and where....Thanks for the help..

 

Did you ty using Windows' "System Restore" to roll Windows back to a previous state when your computer was functioning correctly?

 

I'm running Win7 Home Edition. I have restored to a previous date but still not change. I went as far back as I could, which was only a few months. So far all the fixes for this problem are for Vista and nothing for Win7. Nothing in the Vista fixes match up.