I would go with Windows 7 or 8, not Ubuntu. You will not get much help if you run into issues running Ubuntu, and you certainly will not be able to run off the shelf PC software that you purchase at the local electronics store, such as Microsoft Office, or many popular games.
As for battery, do you mean, power supply?
Any SATA drive will be perfectly compatible with your motherboard. If they happen to use different standards, they will still run at whichever the highest compatible speed is.
Look at what RAM the motherboard supports. If you aren't sure, look at a site such as Newegg.com, or go to the motherboard manufacturer's website and download the manual for the motherboard you are going to purchase. It will list what RAM is compatible with the board, and may even recommend certain brands and sizes of RAM modules for use with it that have been tested by the manufacturer for compatibility.