If you’re not up for spending your money on one of the less advanced smart watch models, you may want to check out maker Jonathan Cook’s DIY Open-Source SmartWatch, part of which is 3D printed, something the prognosticators of future tech surely didn’t forecast. Cook shared instructions for making his SmartWatch on the webzine “Make:” and also on his own website, DoNothingBox. You can download the STL files on the DNB site, too. For around $125 or less you can make your own smart phone and you can customize it, something that you wouldn’t be able to do with a store-bought version.
This is a site dedicated to Linux and so I am of course going to recommend the Linux Mint option. The look and feel will be much like the Windows 7 interface you are currently using. You won't need to upgrade your hardware. You will never be out of support. It won't cost you a penny. You won't need to buy extra software such as Microsoft Office. You won't get any viruses.
Recently Linus Torvalds announced Linux Kernel 3.18.3. The Kernel includes several bug fixes. Latest Linux Kernel includes new features, bug fixes and improve security. Updating/Upgrading Linux Kernel is recommended.