Special ? about Windows 10 Nobody Else Will Answer [View all]

[IrishAyes]

I have great friends on another website (as well as here). Some are very tech savvy, and they honestly mean to answer my question but they still don't although I've rephrased it twice. I hope someone here can do it.

Here's what I posted elsewhere:
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"Tech question! With Windows 10 now available for free download, I've learned some things but still haven't found the answer to a major question.

Okay - if you download and install the program, you have something like 9 months or so to switch back to your previous OS. Fine. You also have up to a year (?) to download and install.
What I still feel unsure about is exactly what happens when you do download. Does the program demand to be immediately installed, thereby wiping out your files etc., or does it download and just sit there quietly until you're ready to install later? I have plenty of room for 10 but also tons of files that I don't have time to move out of potential harm's way just yet."
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All sorts of great advice follows, such as wait the full year allowed to download a free version so the bugs will already be addressed, etc. But no answer to the question I asked! Maybe they assume it no longer matters since they're telling me to wait. But I still want to know!

Part of the trouble is that I don't 100% trust MS to give us that year-long period for a free download. And I do have a massive hard drive with tons of memory so if the download will sit in the corner quietly and NOT auto-install on download, I could easily go through the patch process after downloading.

Oh, and I'm running a 64-bit Windows 8.1 btw.

Thanks for any help you can offer.