Posted: 14/03/2017 at 18:25
It depends what you do with the computer that determines whether or not you need to worry about this.
I have an ancient laptop which is running XP.
I only keep it because I have some family tree software which won't run on my main computer. I don't use it for accessing the internet at all (not even getting or sending emails) - so I have no worries at all about security. I don't even have anti virus software installed.
If you do online banking or buy a lot of stuff online the very least you should have is very good anti virus software installed (and kept bang up to date) - but really you would be better off with a newer operating system. Some banks etc now encourage you to download their own anti virus software as additional security - which you may not be able to do with an older operating system.
If you don't use the internet for financial matters and don't share sensitive data on the internet you would probably be ok with good anti-virus software as KT53 suggests. Many people just use the internet for emails, skype and browsing the internet. That's fine. So long as you're not putting credit card or bank details in you probably won't come to much harm.
Hope that's reassuring