why GC not work?

[mzfhhhh via Digitalmars-d-learn]

import std.stdio;

void testGC()
{
     auto b = new byte[](1024*1024*100);
     writeln("malloc 100M!");
}

void main()
{
     foreach(i;1..100)
     {
         testGC();
     }
}
--------------------------------------
core.exception.OutOfMemoryError@(0)

win7 x86,dmd v2.066.0