We can install an Solid State Disk in to it, as it can improve your boot up times, and opening applications, which can save a lot of time, vs a mechanical HDD.

Over time, Windows builds up useless files that take up space. CCleaner is our favourite disk cleaner and the foundation to a clean Windows 10 system, but it also has many more useful features inside its toolkit.
Aside from cleaning the caches of all kinds of software, CCleaner lets you easily disable startup programs, find which files are taking up the most space, clean up your messy context menu, and create a quick text file of all installed programs.
www.piriform.com

These days it's pretty easy to tell the difference between the legit emails and the non genuine copy. To be sure however, you can check the email address by looking in the sender section of your email client. (Applies to Mac and PC)

This depends on where and how as much as it does when. Our rule of thumb is try to keep two copies of everything valuable. One in the cloud (One Drive / Dropbox etc) and one local on an external disk that you unplug afterwards.

Most of the time you should be fine to just remove them, if you are using a Windows computer, as Windows 10 does a better job to avoid data loss when compared to Mac OS X or Linux