As long as you follow these instructions, you should be able to do whatever you want with the data that's on there right now while still being able to boot into the new installation of Windows 7 once the old HDD is removed:
Now, I suspect that you will want to avoid reinstalling as many things as possible, but unfortunately almost everything will have to be reinstalled in order for them to work properly. However, you may be able to lean on OCN to find out what needs to be reinstalled and what doesn't by making a list of everything that's installed right now that you would rather not have to reinstall.
So ultimately, it's actually a very simple process.
Another question. Might upgrade everything sometime around October, which would mean a new mobo. As long as I get the full version of Windows 7 and not the OEM one right now, I'll be able to install it again on the new build right?