Ok, but do you understand you weren't hacked?
The client generates new addresses automatically. It's going to do that regardless of whether you get a new wallet or not.
The bitcoins you currently own are in the original wallet file that was in that directory. So do not delete or lose that file.
No. I have been involved with BTC for a while and never heard of a wallet changing its address. My question remains... how do people know where to send money to me ( or anyone else ) if the address is changing?
I looked in the blockchain... and there is no connection with the new address.
It doesn't 'change' its address, it shows you a different one for convenience, that's all. As long as you keep wallet.dat you will have all the addresses it ever shows (and 100 more already made btw that you can't see).