I’d recommend you installing Ubuntu.
You won’t need neither to use a VM nor to erase Windows.
Go to Ubuntu site and download wubi (it’s a windows installer).
It will install Ubuntu in the HD. On boot time you chose either windows or Linux. This way you’ll have 100% memory and processor for the operating system you’re using at the moment.
It will take at least 5GB and at most 30GB of your hard disk (you chose how much space you want to let Ubuntu use at the moment you will install it).
My own experience is that to develop for Android is a nightmare when one uses C/C++ no matter whether one is using Linux or cygwin… but believe me: it’s better to have a Linux than to use cygwin.
Note: wubi may automatically download Ubuntu iso, but I strongly recommend you download the iso yourself and put it in the same directory with wubi. This way it will use the version you’ve already downloaded.