You cannot just borrow a Windows disc from your friend and expect it to run.
One licence, one computer. That's the rule unless you buy a licence for more than one computer.
If you want a trouble-free Windows 7 experience, you'll need to buy a genuine copy of Windows with a genuine product key.
I'd advise treating Amazon and eBay with great caution. Your best bet is to buy direct from the Microsoft store.
This the link for the Microsoft Store in Egypt. http://www.microsoft.com/middleeast/egypt/windows/shop/