I donot exactly remember maybe I had emailed it to myself using yahoo mail. . This is a wallet from early 2011, and it was created as a hot wallet on a windows computer. I was amazed that some thief could get a copy of it from somewhere. It's a Windows 7 computer. I am now using armory. Are you aware of tools to check for hidden keystroke loggers? I guess the best secure solution is an offline wallet.
STOP USING WINDOWS. Also don't email an unencrypted wallet. In theory a devious yahoo employee could search for attachments containing wallet.dat
Go download some linux. Install it to a big flash card or usb drive/stick. Or learn how to partition your hard drive and dual boot. Only install bitcoin on the version of linux. Don't mail your wallet to youreself unless its encrypted. you will keep coins secure.
Thanks for the suggestions.
All my miners are Linux. in 2011 bitcoind and bitcoin-qt did not have encryption features. I have now created a new wallet and immediately encrypted it. I am concerned that there could be a keystroke logger on the windows pc. You are right I should keep all wallets in *nix pc.