How to upgrade a 17" Macbook Pro from OS X 10.6.8 Snow Leopard to Sierra or High Sierra?

MacBook Pro models that can run Sierra and High Sierra. Your model will run El Capitan, but that is as far as it will go.

Upgrading to El Capitan

You can upgrade to El Capitan from Lion or directly from Snow Leopard. El Capitan can be downloaded from the Mac App Store for FREE.

To upgrade to El Capitan you must have Snow Leopard 10.6.8 or Lion installed. Download El Capitan from the App Store. Sign in using your Apple ID. El Capitan is free. The file is quite large, over 5 GBs, so allow some time to download. It would be preferable to use Ethernet because it is nearly four times faster than wireless.

Macs that can be upgraded to OS X El Capitan

1. iMac (Mid 2007 or newer) - Model Identifier 7,1 or later

2. MacBook (Late 2008 Aluminum, or Early 2009 or newer) - Model Identifier 5,1 or later

3. MacBook Pro (Mid/Late 2007 or newer) - Model Identifier 3,1 or later

4. MacBook Air (Late 2008 or newer) - Model Identifier 2,1 or later

5. Mac mini (Early 2009 or newer) - Model Identifier 3,1 or later

6. Mac Pro (Early 2008 or newer) - Model Identifier 3,1 or later

7. Xserve (Early 2009) - Model Identifier 3,1 or later

To find the model identifier open System Profiler in the Utilities' folder. It's displayed in the panel on the right. Are my applications compatible? See App Compatibility Table - RoaringApps.

You are welcome. The newer OS versions are free. You don't have to buy them. Whether you can upgrade to High Sierra depends on how old your computer is. You first need to upgrade to El Capitan using the link VikingOSX posted.

To check the model number hold down the option/alt key, go to the Apple menu and select System Information.

macOS 10.12/10.13 (Sierra/High Sierra) require one of the following Macs:

MacBook Pro (Mid 2010 or later) Model 6.2 and higher

How to get macOS High Sierra

Check to make sure your applications are compatible. PowerPC applications are no longer supported after 10.6.

Application Compatibility

El Capitan 10.11 Compatibility information

Also check to make sure there is a compatible driver for your printer.

Do a backup before installing, preferable 2 backups on 2 different drives.

Try contact iTunes Support to enable your old ID/password in the App Store. Either use the form or scroll to the bottom of the page in the 2nd link. Follow through the screens to get a chat or telephone option.

iTunes Support

iTunes Support – world wide

If you have the means to put a new SSD into that 17 inch Mac Book Pro, then do so because the performance difference will be simply astounding, and Sierra and High Sierra are written to assume they installed on an SSD. People have been having issues with Samsung SSD and High Sierra, so go with something from Mac Sales, or Crucial to play it safe.

If your MacBook Pro is a mid-2010 or newer, it meets the hardware requirements for High Sierra. However, it sounds as though the Apple ID/password associated with the current installation is no longer valid, and that presents a problem.

In order to get a current Apple ID associated with the operating system, you will need to reinstall from the installation DVD that came with the MacBook Pro, and fully update through 10.6.8 so that you have the compatible Mac App Store and associated current Apple ID/password. When Snow Leopard asks for your Apple ID, use your current one. High Sierra has a 10.8 existing installation requirement, so you will have to subsequently reinstall El Capitan after Snow Leopard with the current Apple ID.

Here is a link to El Capitan from the Mac App Store. Sign in with your current Apple ID. Once this is installed and all updates are applied via the Mac App Store Updates panel, then you can get High Sierra from the Mac App Store in a normal manner.

I operated off the premise that the OP's MacBook Pro was a mid-2010 or later device, and Sierra/High SIerra hardware specs allow for the mid-2010 or later MBP.

Am I wrong?