ok booted neon 5.21.3 using ventoy on my low spec, but 64 bit uefi laptop. To be fair quite a nice looking Distro. Quick and responsive , which recognised my wifi card ( always a plus) .
So couple of things :
1: ) you need to confirm whether your PC is 32bit (you might be wasting your timer trying to install) or 64 bit (worth a try)
2) I went throught the inital stages of install , pulling out before it did anything to my main OS (Slackware) .
If you look at the images i've attached it states , select "storage device" . What it really means is select where you want to install. Now /dev/sdb is more than likely a usb stick attached to your PC, in addition to the usb , you had neon on.
If your PC , had uefi i.e had an EFI partition , then you would see similar to my image and you would just mouse left click on down arrow to find your /dev/sda However , you will have to make a selection best to your PC
So basically unlike slackware , where i have to use a terminal to do everything you have a nice , visual graphic installer. On your system you could delete /dev/sda6 and /dev/sda7 then you can use Gparted to use both the created free space into one partition of around 170 gig. If you don't do that then you will have to choose to install Neon on either the 128 gig /dev/sda6 or be probably cramped onto /dev/sda7
Or i guess use the gui installer to stretch , shrink as necessary ( but be careful)
So to summarize if you have a 64 bit PC , you can boot up Neon and play around with it or click on install icon. I , if i where you get to live boot stage and play with it, then consider where install is going ; get back ups for Windows in place etc , read up on manual partitioning
Now as for grub , yes you install it to /dev/sda , if thats where your main install is going , along the lines from a terminal of :
Code:
sudo grub-install /dev/sda
then you run :
that should add Windows OS to grub boot menu; however you probably won't need to use terminal, at one point in graphic install it will give you choices
if you have any questions - feel free to ask. I will probably be back some time tomorrow