A:AnswerGood question. You cannot purchase this computer with Windows 7 preinstalled. It comes with Windows 10 so you cannot downgrade to another Windows edition.
I hope this helps.
A:AnswerGood question. This computer has 1 PCI-E x 0.5 mini socket slot (occupied). This computer is not a good choice for upgrades. It is an entry level desktop for everyday tasks. For more detailed specs, please visit the following link:
http://store.hp.com/wcsstore/hpusstore/pdf/t4a12aa.pdf
I hope this helps.