Fireworks' magnification has always worked around presets. If you want something other than those presets, use the Zoom tool to draw a marquee around an area on the canvas.
You can check out this free extension on the Adobe Exchange which should give you more control, though:
I downloaded the extension and now got another issue. The installer
says I need Fireworks greater than version 6. I have version 220.127.116.11
Maybe this is the run as admin issue on Vista?
Jim thanks it was that run as admin issue on Vista32
I spoke to soon. It did install but I can't find it. Here is the doc on it:
To open the Numeric Zoom panel, choose Window > Numeric Zoom.
It is not there??
Did you restart Fireworks? Many extensions require a restart before they become available in the UI.