im on zorin right now...
I decided to get new HD and do a clean install, then transfer what I needed from windows. so far so good.
****make sure ya have backups of everything just in case if ya try to dual boot
bkmk
Are you using GParted to do the partitioning? That will allow you to make your changes and inspect them before “pulling the trigger” so to speak. Anything can be undone up until that point. The thing is, you have to use a LiveCD or DVD to do that. Unless things have changed since I installed Linux some years ago.
Tech Ping
It is safer to make space for Linux by shrinking the Windows partition from within Windows, using the Drive Management dialog. The blank space is then called “Unallocated.”
The Linux USB will recognize that Unallocated space and offer to install there.
Linux Mint usually handles partitioning without manually messing with partitioning. I never had problems with installing Mint on BIOS-based systems.
I don't think the T520 is new enough to have UEFI. Should be standard/legacy BIOS. Should be able to just install it straight away. For booting to USB on a thinkpad, you can change boot device to USB in the bios as you have or you can hit F12 when booting to choose a device on any given startup. Just FYI.
I've never done a dual boot setup with two drives so I don't know how or if that would work. If you don't or can't do a dual boot install, you'll have to choose a hard drive to boot to every time you start the computer, hence the F12 trick. Dual boot on a single hard drive gives you a new menu that comes up after initial boot called the grub menu. I always just install alongside windows but do it the manual way. Instead of choosing "install alongside windows", I choose "do something else" so that I can choose partition sizes etc.
Regarding gParted. It's likely that or another disk management program behind the scenes on the install screen. No matter, they all work the same. Here's a good tutorial with screenshots as far as making the partitions that might help you. https://www.linuxtechi.com/zorin-os-15-installation-guide-screenshots/ - You can choose your own partition sizes of course. For linux, always format to ext4.
Found this on installing dual boot with two drives and/but it's for UEFI, https://askubuntu.com/questions/726972/dual-boot-windows-10-and-linux-ubuntu-on-separate-hard-drives#843649
Install on a USB stick and boot with it or install onto a VM. Our Java development environment is a VM with Ubuntu
I second what PastorBooks said. If you are going to dual-boot you need to defrag that Windows file — get it as small as possible so you know exactly what you’re dealing with space-wise.
My first Linux installation was a dual boot with Zorin Lite 9.0. I still have that laptop but it was the last time I dual booted. I was trying to preserve my Apple iTunes software which pretty much doesn’t play nice with Linux.
Lenox, Linux or Lennox (Annie)?
I’m on Zorin. Loved it at first. Fast and reliable. Then after a few updates it started getting quirky on me. Videos would freeze up for no reason (audio kept going though). It logs me out of everything about every 10 days (probably a safety feature). I’ve stopped the updates and am living with it but either need to do a new install or go with Mint.
Don’t take this the wrong way FRiend but it seems to me that you’ve made a strategic mistake but you’re asking about tactics. Based on your knowledge and experience you should be gaining experience with partition tables, file systems, boot logic in a sandbox that if you mess up won’t have any dire consequences. If you keep going in the current direction you might get lucky and get Linux to happily coexist with your production system but it wouldn’t take much in terms of misconfiguration or false steps to brick your current system.
I’d strongly recommend getting 5 to 10 Linux installs under your belt first on some other, separate hardware or on a virtual machine.
Back up your data and then let Linux erase your Windows.