Bonjour Mike,
This is because you are probably using a 1280x1024 resolution, so you loose parts of the UI.
You can arrange this manually by doing Layout > Edit Layout. You will some areas highlighted with red, just drag those red lines to resize the layout parts. When you're finished do again Layout > Edit Layout, and overwrite the default layout (Softimage Suite user).
If you don't want to bother with this you can simply download an already done layout at this link:
http://www.edharriss.com/xsi/Layout\_presets/layouts.htm
Scroll down until you find the 1280x1024 layout (it's near the bottom of the page), click on the icon and drag it on the XSI interface (you will see that your pointer changes).
Hope this helps
Salutations - Cheers
Bernard Lebel