One reason for the Win32 calls for file handling is that on some platforms 
the vanilla fseek etc are not available (e.g., WinCE).  So say the comments 
on one of the files, at least.

Also, there seem to be extended versions of the Win32 calls that work more 
directly with 64 bit integers; these might be easier to work with.  There 
is a structure designed to make handling the 2 32 bit word approach easier, 
but I suspect it might interact poorly with the rest of the squeak system.