Re-installing Windows: a couple of comments...

It's easy, if you have the installation DVD, and if you haven't, there's help... Let's give you an example. Yesterday, I met Steve, our on-site Maintenance Man, who had just come out of a next-door apartment, diagnosing a plumbing problem. Steve asked, "Hey, Ray - you're handy with computers - how can I get a copy of XP Pro with its updates, to put into an old single-core Pentium-4 PC that I found in the big bin, and looking OK...?" And I said, "Let me look on the web for you, and see what I can find, and I'll get back to you." I looked on the web, and here's what I found:-

This website has all sorts of free downloads, including full operating systems, but without the required key codes, because, as they so rightly say, Microsoft would only nullify those anyway, and if you need a code, and you will, then just buy one like the rest of us do.

Anyway, I found that they have an .iso of XP Professional, with its SP3, and also with its updates to November of 2013, and also including SATA drivers. So I downloaded that .iso, burnt it to disc with ImgBurn, and gave it to my friend. He already has key codes for it, he says, so that ought to solve his problem. Maybe. There's also the problem, of course, that XP is no longer supported, and this means a security problem possibly. But there are solutions for that one.

Re-installing Windows, in my case most recently, Windows 8.1 64-bit, the big nuisance for me is not the installation itself, but replacing all my third-party programs collected from hither and yon. With three operating systems on here, it's easy to go into another one, and drag-and-drop a program from it onto the desktop of the newly re-installed one. That's great for getting something going in a hurry, but it means you can't find it on your Default Programs list where you want to have it, so it can be configured correctly. Simply putting your dragged-and-dropped program into the Program Files folder doesn't do it - it has to be downloaded from somewhere and then freshly installed, to make it show up in your Control Panel's 'Programs and Features' and in your 'Default Programs' lists. 

So the old drag-and-drop trick works to get a program from one operating system to another on the same drive, so you can use it right away, but it has to be installed the normal way to make it show up properly in your system and be configured there to work with everything else. Just an 'FYI' Kiddies.