"IZoom does not have all the features that the more expensive commercial magnification software products have. It works best at a resolution of 800 x 600 or less and with 16-bit colour or less. The tracking is not entirely consistent. The focus will follow the typing caret and the mouse cursor. When tabbing around icons on the desktop, however, or when using Alt + Tab to change program, the focus does not follow the highlighted screen area. It does also slow down the PC when it is running, and is limited to Windows 2000 and XP only; there are many Windows 98 users still out there."
How much maginification do you need? FastStone Capture click here has 300% zoom tool which is pretty good. Shift PrintScreen will zoom the whole screen by up to 300% It is also very useful for taking screen shots. I load it at Windows startup, so its always available. It takes a second or two to load the magnifier and it is only temprary (until you click somewhere), but I don't notice any stability problems. The hot key for the maginifier can be changed to what you want.