OSX Sierra on a 2008 Mac running OSX Snow Leopard?

[Logical]

I have a perfectly functional 2008 MBP running Snow Leopard. Once upon a time I tried upgrading to Lion but that just about killed my poor computer, so I went back to Snow Leopard and I never want to upgrade it again. I am sure it would not be able to run Sierra! But I wonder if it would be possible to use Virtual Box on it to run Sierra. I might want do to this because ALL browsers (Firefox, Safari, etc) are unsecure on Snow Leopard nowadays (no more security updates). So, maybe I can put Sierra on Virtual Box on my Mac, and then use browsers inside of Virtual Box. Is this possible? Sierra is free, right? Will it work? Will browsers in Virtual Box be secure then, even though the real computer itself uses Snow Leopard? Any thoughts?

[socratis]

I have a perfectly functional 2008 MBP running Snow Leopard.

Please post the exact MBP model and its configuration, mainly RAM and HD (total and available).

I went back to Snow Leopard and I never want to upgrade it again.

I know exactly your feelings. My early 2011 MBP 8,3 can handle up to 10.12 easily, but I was running 10.6.8 up until 1 1/2 year ago. Now I'm on 10.9.5, but I suspect not for too long...

I am sure it would not be able to run Sierra!

Most probably not. At most you could go up to 10.11, El Capitan. See: https://support.apple.com/kb/sp742, https://support.apple.com/kb/sp728

I might want do to this because ALL browsers (Firefox, Safari, etc) are unsecure on Snow Leopard nowadays

You might have to download Firefox 45.8.0 Extended Support Release (ESR), which is developed and updated almost in parallel with normal Firefox and will support 10.6, up until Jun/2017. See https://www.mozilla.org/en-US/firefox/o ... tions/faq/ and you can download it from https://ftp.mozilla.org/pub/firefox/rel ... .0esr/mac/

So, maybe I can put Sierra on Virtual Box on my Mac, and then use browsers inside of Virtual Box.

It's going to be a real pain. Honestly. Your MBP is quite old and virtualizing an OSX guest is not the fastest process in the world. Plus, I'm not sure that it will work given your CPU. And you can completely forget about audio/graphics intensive sites. No WebGL for you and it's going to be crawling.

Will browsers in Virtual Box be secure then, even though the real computer itself uses Snow Leopard? Any thoughts?

I was testing 10.9.5 on an external HD and restored my files from a TimeMachine backup. I then tried it the actual MBP (switched the HDs) but without a network as to avoid messing any online account. I kind of liked it/forced to use it. I never switched the hard drives again and I'm stuck ever since.
I suggest you try to upgrade your "dead" OS. You have a lot more to worry about compared to up-to-date browsers.

[loukingjr]

I agree with everything socratis had to say.

Personally, I don't try running any OSX guest in VirtualBox. What I think is you should save your pennies and get a 2012 or later Mac. A refurbished one from Apple will do.