In Opera, it's right button down, left button click to go back, left button down, right click to go forward. Always.
It's the same in Firefox, until Firefox gets updated and the gestures plugin is broken for a few weeks until the maintainers fix it for the new firefox version.
Going to IE is a nightmare. Then it's right click, click Back on the right-click menu.
Once you get used to mouse gestures, you wonder why anyone would ever waste so much mouse mileage going up to the Back button all the time.

Why not move to Linux?
Maybe because 99+% of all significant applications used by businesses have been built for Windows.
Or do you think it would be trivial for every software vendor out there to drop everything they've been working on for the last 20 years to switch platforms?

But if you follow the links to download, they go back to pgp.org where you have to pay $$$$

I've kept a copy of the installer for the freeware version of PGP before they started getting uppity about it.
Works on XP just great. Version 8.0.2.... dunno if this version is still found in the wild....