1) ftp.heise.de/pub/ct/spezial/spice3f4.zip
SPICE 3f4 compiled by Wolfgang Mües for Win32.
There are no limitations of number of parts or nodes and you may use and distribute it for free.

2) LTspice/SwitcherCAD III
Updated october 19, 2007.
It is free and it seems to be unrestricted.
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Peter