funkajunk

1. The actual time needed to wipe out Windows and install is under 30 minutes.
2. See above.
3. Prebuilt machines use OEM keys, which are $10-$20 at best - whoever you buy the system from is definitely getting a volume discount. In my opinion, a small sacrifice to be free of M$.

Pretty much all modern Linux installers offer to wipe the existing drive and overwrite. Just prepare a USB drive and boot from it, then follow the steps in the wizard.

Create bootable media - Linux Mint

One of the few things that accursed software actually got right!