Basically, your wallet's hacked. Someone gained access to your private key & they did spend all of the btcs in it. The same case did happen with meh a few days ago. However, the best thing that you can do is to format your computer & start with a new wallet (like meh) & you'll be fine. Simple as that. Take that as a lesson & next time dont download random things over the net.
Just to add to this answer: most likely, you are 100% correct, altough it's usually done by a keylogger, or remote controll software that has infected your pc... not by really hacking the wallet. Just to be clear: if you used a password to protect your wallet.dat and your pc is clean, chances of a wallet getting hacked are very, very slim.
A couple lessons:
- always use a virusscanner, malware scanner and a firewall
- password protect your wallet.dat
- if possible, use a hardware wallet or paper wallet
Basically, your wallet's hacked. Someone gained access to your private key & they did spend all of the btcs in it. The same case did happen with meh a few days ago. However, the best thing that you can do is to format your computer & start with a new wallet (like meh) & you'll be fine. Simple as that. Take that as a lesson & next time dont download random things over the net.
yes i didn't use any password i didn't know about this feature 
i wil do a clean or a format i see i saved my dat file to a local folder looks like someone access this file and while it isn't password protected
That can indeed be the problem... If somebody manages to download your wallet.dat and you didn't use a (strong) password, the attacker could have transferred all your coins to his own wallet.
You made two mistakes in your setup: you allowed somebody to have access to your wallet.dat, either by saving it in a "wrong" place, or by letting your computer getting infected. A second mistake was not to password protect your wallet.
Luckily for you, the damage wasn't that big, you should learn from your mistakes, and make sure you never lose a coin again
