For Q1 - If you don't have the windows update run on the machine even once, or accepted to run "Genuine advantage test" when you visited the Microsoft websites, you can't figure out whether your Operating System is a genuine one. The labels wouldn't appear as in advice above. The best way is to check online using the genuine validator. Below is the url. http://www.microsoft.com/genuine/validate. Navigate there, and click on "Validate" and you will see the result.
For Q2 - Run Microsoft's Direct X Diagnostic tool. Type "dxdiag" in your run menu and press the enter key. You will find a window like below. Go to the "Display" tab, and you will find the device installed in the left section and other details pertaining to it. There are other easy ways to figure this out in Windows 7, but this tip works for all versions.
For Q3 - You cannot retrieve this from a lower priveleged account. However, for the sake of completeness, if you type rundll32.exe keymgr.dll, KRShowKeyMgr in run menu and follow the captions on the buttons, you will see the saved passwords.
For Q4 - There is no use building a list of files as they vary from Operating Sytem to Operating System. It is better you hide the System and other operating files from your normal view, and do a system restore/repair when the system fails to boot. To hide the operating files, follow these steps.
a) Go to control panel - Folder Options. Go to view tab, and check the option as shown below.
Hope this helps.