I don't use linux (yet) as my main OS as a lot of application and games are sadly not compatible with Linux,but i use it
in a virtual machine when i do my online banking as its supposed to be safer.
Yes you can upload it and install Linux on your old laptop:the linux installation will take care of installing itself your new hard disk.
You can download Linux Mint here:
https://linuxmint.com/
There are other distribution of Linux but for a Windows user Linux Mint is probably easier
to migrate to.
With the downloaded .iso image of LinuxMint you burn it to a DVD that will be bootable with your old laptop or transfer it to a
USB key but with an old laptop you will probably not be able to boot from USB as this option is only available on recent
computer.
The burned DVD will also be a "live DVD" that can be used to try Linux Mint on your old laptop without installing it on your
hard disk: it will be slower as Linux will load the files from the DVD instead of the hard drive.
You can also dual-boot (you get windows and linux on the same computer) but that is a fairly complicated option if you are not
experienced with installing operation system.
The main advantage of this option is that you can safely surf the net with Linux and use Windows for your old application
that are not compatible with Linux.
Sorry if this sound complicated:Hornet has been playing with computers for the last 25 years as a hobby
and has been obsessed by them since then...