My recommendation would be to write a file of the SQL commands.
Then use psql -f filename.sql to actually do the inserts.
I am pretty sure you are reading the entire file into memory at one time, which will not make Windows very happy.
Split the 400MB file into 4, 100MB files using a file split utility.
This is available on Unix (and is probably already installed) and searching for "Windows split file" on Google will turn up many freeware tools to do this on Windows.
