Help with NX2
Never buy 'Home' anything. Get Win 7 Pro 64-bit, then you can always upgrade to tons of RAM. Originally get two matched sticks of RAM for dual channel operation, at least 2x2GB.
There is nothing wrong with Home Premium. The only thing you miss from Pro is the ability to join a domain and a free copy of an XP VM "XP Mode". Feel free to stick with what you have for an OS.
I would second the advice to move up to at least 4 GB of memory. Working with the very large RAW / JPG images of an D7000 will be much improved by more RAM.
Win7 Home will support more memory that your motherboard is likey capable of accepting, so no worries.