How to release memory? (D2.0.30)

[AxelS]

Hello everyone,
I've got a problem with the following (very simple) code:

void foo()
{
      void[] dat=new void[50_000_000]; // allocate 50 MByte of dummy-data
      delete dat;
}

after I called foo() and watched the memory usage in the windows taskmanager, 
the program blowed up to 50 MBytes although I deleted the allocated memory...

Why can't the GC remove that data and how CAN I remove it?

Thanks in advance!