Hi Gemma,
There are many people in the same situation as you. The first question you have to ask yourself is what you use your computer for? Is there anything 'special' that needs a particular piece of software which runs only on win whatever?
In the linux world there are essentially two flavours: Red Hat or Debian. They differ primarily in the way software is installed (called packages in linux speak) and the desktop which is installed by default. The key thing with any open source software is how big and active is the community that uses the software as that drives how quickly problems are solved and how easy it is to get help.
Red hat is very popular for server use. The key flavours are: Red Hat Enterprise Linux 'RHEL'(paid for), Fedora, Centos and Scientific Linux. Fedora is a used by Red Hat to test features for RHEL and has a very short lifecycle, Centos is just RHEL without the Red Hat branding and paid for support and probably the one to go for if you like the Red Hat way (its the one I use).
In the Debian corner, there is Debian itself, but by far and away the most popular linux for desktop use is Ubuntu. others are Mint and MATE. Zorin is a derivative of debian/ubuntu, but given the look and feel of windows. The issue for me is that it may have quite a small user base so if you get stuck help may be limited compared with Ubuntu.
There is quite a controversy in the linux world about desktop interfaces, with Fedora /Ubuntu moving to towards a more tabletty interface whereas Mint or MATE have a more traditidional desktop by default. Of course with everything linux there is usually a choice - so depending on your appetite for geekyness change is possible.
Almost every flavour of linux offers a live desktop and if it doesn't that is a bad sign. This allows you create a bootable CD or USB stick and try it out without having to install it onto your PC.
So my suggestion would be to down load a couple of alternatives and try them out and see which one you like most.
HTH
EG