linux is free. and very user friendly now. it will be new, but any windows user can figure it out. no it's not like something from the 80's. in fact windows is something closer to the 80's than linux.
linux is also 100% customizable. there's things you can do to linux that microsoft does not allow. yeah, it's that customizable. you can even choose what kernel you want to run. with windows, you use what microsoft says you can run. linux will run on a old computer hardware and make it feel as fast as a newer computer. linux just gets out of the user's way. it doesn't hog system resources like windoze does. it wont sit there and scan the drive for 15 mins and hog up so much of the system resources you have to wait for it to finish. it wont do updates that make you restart and then take 30 mins to install them before it boots back up.
it will be a slight learning curve and you will need to read a bit about linux and a little getting to know linux. but if you can figure out a smartphone, you can use linux.
if youre comfortable installing an operating system which they made as easy as installing software then you can install linux. it will install itself and leave windows untouched if you want to keep it. when it boots up you can choose to run linux or windows. linux can see a windows files system so you can access your files from linux.
I would recommend Linux Mint or Ubuntu for beginners. they both have a complete set of office software called libreoffice (you can download it for windows too, it's 100% free), dvd/cd burning software, internet browsers such as firefox and google chrome. several email apps such as mozilla thunderbird (makers of firefox) linux works best with brother and Hp printers. both companies offer drivers for linux. cannon is pretty much a no go. and epson is hit or miss. linux has an "app store" to find all the software you need to do pretty much anything.
if you're an average PC user and mainly just get online for stuff or occasionally use microsoft word and watch youtube, facebook, banking, etc etc, it's excellent for all of that. it can do much more but most of us do not use our computers for more than that.
just for example, microsoft has admitted they use linux on their own servers. it's just that much better.