Will the free Windows 10 upgrade delete all my files and data?

It should only affect the Operating System itself, and Drivers.

It is free now, because users now are testing it for faults not because they are being gratuitous. You will be finding the bugs for them to fix or not as they please.

I have a 500$ laser printer sitiing under a dust cover from when they went from Vista to Windows 7. The Xerox people never upgraded their drivers so it will not run anymore.

I say IF you have no reason to upgrade Do Not Do It.

Be sure you will be gaining some new feature you cannot live without. Otherwise wait until you buy your new computer with it.

Look how poorly the Windows 8 treated prior users and older games.

The update failed on mine, and I got the "Failure configuring Windows updates. Reverting changes. Do not turn off computer" loop. I ended up fixing it by refreshing my PC in the recovery options for HP. Sadly, I lost files when everything was fixed. I haven't had a successful update to Windows 10 though.

Should not, but to be on the safe side back up your files and data to an external hard drive.

Yes. So you first need to back up all your data on an external hard drive and then do the upgrade.

It's an in-place upgrade. All your programs and personal files will be transferred automatically. One should always have backups of important files regardless.

It's best to back up all your files before trying windows 10, if not mistaken once windows 10 is install all your files will be gone

It's not supposed to. But I would back everything up anyway and do a clean install. I think that would just work better.

If you have important files on your PC, and they are not backed up regularly, then BY DEFINITION they are NOT important to you.