You can make use of your wheel mouse or the up and down arrow keys on your keyboard to zoom your desktop.

By hitting a customizable keyboard shortcut, ZoomIt will be activiated. It does not require any additional windows to open or close.

Besides the zomming features, ZoomIt can be used to draw on your desktop (with or without zoom), using a customizable color and pen width.
It is a presentation aid, with a draw feature that allows the presenter to circle or highlight part of the screen display, and a simple push of the “E” key erases the drawing again.

It also includes a customizable break timer that will blank your screen with a countdown.

ZoomIt can be obtained from following URL

http://technet.microsoft.com/en-us/sysinternals/bb897434.aspx