To play several accounts at one time on the same computer, download the client from Runescape's main site. Open two windows and get to the login screen on both. Then, shrink one window. To match the "Login" button with the background screen, enter your name and password on both screens. When you login, click the "Login" button on the top window, and quickly press the "Login" button on the background screen. The game only allows 30 to 60 seconds before you are logged due to inactivity. Make sure you use both windows frequently. It is best to use ALT + TAB to switch back and forth between the windows.