Your mouse has primary and secondary buttons. You use the primary mouse button—usually the left button—to select and click items, position the cursor in a document, and drag items. You use the secondary mouse button—usually the right button—to display a menu of tasks or options that change depending on where you click. If you're left–handed, you can reverse the buttons and use the right mouse button as the primary button. Here's how:
Click the Start button, and then click Control Panel.
In Control Panel, make sure you are in Classic View, with all Control Panel icons showing. If not, click Switch to Classic View in the left pane of Control Panel.
Click Mouse to open the Mouse Properties dialog box. Click the Buttons tab for the Buttons configuration box. Select the Switch primary and secondary buttons check box. Click OK.
Click OK, and then click the Close button in Control Panel.
Display the Start menu by pressing Ctrl+Esc (or the Windows logo key). Then open Control Panel by pressing C.
In Control Panel, make sure you are in Classic View, with all Control Panel icons showing. If not, go to the left pane of Control Panel and open Switch to Classic View by pressing Tab and then Enter. Press the arrow keys to move to Mouse, and then press Enter.
In the Mouse Properties dialog box, on the Buttons tab, you'll see the Buttons configuration box. Select Switch primary and secondary buttons by pressing S. Then press Enter.
Close Control Panel by pressing Alt+F, C.