current implementation of file uploads
requires the uploaded form data including 
the file data itself to be completly held
in memory for a short while

if your file gets to big it may exhaust 
the available memory on your system

to prevent php from bailing out here you
should set a lower limit for upload_max_filesize 
in PHP init and/or switch to an operating system
with better memory handling capabilities than
the still somehow DOS-based Win95/98 line

PS: moved to change request as there should be
a more clever way to deal with post data than
to stuff it all into main memory ... i think i
remember Rasmus talking about someone working on 
this when we met in Brussels

This should be fixed in CVS now. You can try the latest 
development build from http://www.php4win.com/ but
make sure it's dated after 27th of October 2001.

Also, there are some minor leaks still in the new code.
If you encounter such leaks, please send the shortest
possible code + html with which you can reproduce the leak
to php-dev@lists.php.net (or me) so we can get rid of these leaks. 

This fix will be in PHP 4.2.0.

--Jani