Will Windows 10 be an upgrade to Windows 8.1 or a fresh OS install?

[Kayvim]

I wish to specifically know if installing Windows 10 cleans and rewrites the registry wiping out all my installed programs or modifies the registry and maintains the installed programs?

 

[ttsoldier]

No it will be an upgrade.

 

[hotphil]

No it will be an upgrade.

It depends how you run the installer.
If you do an upgrade, it will try and upgrade.
​If you tell it to do a fresh install, it will try and do that.

 

[owensdj]

From what we know so far, it looks like you'll need to do an in-place upgrade from Windows 8.x/7 to 10 if you want to get the free upgrade. After that you can choose to do a fresh OS install of 10 at any point. Of course you can also buy Windows 10 for new devices and do a fresh OS install.