Use command prompt is also an easy way to reset lost sa password. See the commands below:
Method 3: Use Command Prompt to reset your lost SQL sa password
Step 1. Open a command prompt (Start -> Run -> cmd)
Step 2. Type the follow commands, and press Enter after each line:
Osql -S yourservername -E
1> EXEC sp_password NULL, 'yourpassword', 'sa'
Of course, you can reset your other sql account password, just by changing the 'sa' to your another sql account name.