In Windows 7, there's a window auto snap feature called Aero Snap. When you drag a window to any edge of the screen, it automatically snap and resize the window. Also, holding the ❖ Win key then press any of the arrow key also works. 〔☛ Windows Logo Key Keyboard Shortcuts〕
You can turn this feature off.
To turn it off, just go to the Control Panel, “Ease of Access Center”, then the “Make the mouse easier to use”.
Note that this will also turn off the snap feature using keys. That's too bad, because i would like just the mouse activation off, but the key such as maximize by 【❖ Win+↑】 and minimize by 【❖ Win+↓】, and snap to side by 【❖ Win+→】 and max only vertically by 【❖ Win+⇧ Shift+↑】 … etc are quite useful. Some of these you can do by 【Alt+Space】 then n or x but isn't as convenient.
Extra tip: 2 things i find greatly useful is: ① making opening file with a single click. I think double-clicking is from the 1990s and should be eliminated. ② Make the window automatically come to front (auto-raise) when mouse hovers over. This will take some used to. (you'll get into the habit of not to move the mouse pointer when you don't need to)
The above will save you many clicks, especially if you use computer all day and is risking RSI (repeated strain injury). For how, see: Windows Auto Raise; Single Click to Open File.
Another trick i must have is: Swap Mouse Buttons: Right-Click ＆ Middle-Click, while in web browsers.