Memory allocation failed. Why?

[MGW via Digitalmars-d-learn]

import core.sys.windows.windows: MessageBoxA;

void test() {
        for(int i; i != 10; i++) {
                ubyte[] buf;
                for(int j; j != 100000000; j++) buf ~= 65;
                MessageBoxA(null, "--on for--".ptr, "".ptr, 0);
                // delete buf; // if ON - then memory delete in step
        }
        MessageBoxA(null, "--off for--".ptr, "".ptr, 0);
}
void main() {
        test();
        MessageBoxA(null, "--The end--".ptr, "".ptr, 0);
}

----------------
core.exception.OutOfMemoryError@src\core\exception.d(693): Memory 
allocation failed
----------------

Simple program and error. Why?  Windows 7 (32) dmd 2.072.0