Most of these (but not all) are free for personal use only. Please ensure you comply with their license terms.
Be CAREFUL to find and choose the free version as some links have versions that you have to buy. Free versions of some software will attempt to up-sell you to the paid version, none of those below make this compulsory but some try really hard to make you think that it is time you paid!
I prefer some (but by no means all) freeware products to the real paid for stuff!
Anti virus and other undesirable stuff( you should definitely have one and only one paid or free)
If you do on line banking with Barclays you can get free Kaspersky Internet Security which is very good anti virus and firewall protection if somewhat slow.
Firewall ( you should definitely have one and only one paid or free)
Paid anti virus products also often include a firewall so you shouldn’t add any other firewall product. Otherwise, one comes with Windows XP and later - its not great but your router is probably firewalled too. This is probably the best option for many people who will often just be confused by the best Firewall products. If you understand what is being asked Comodo Firewall is probably the best.
Internet content filtering
Open DNS (you don’t install this which makes it very light on your PC) and K9 Web Protection can prevent undesirable web sites from loading.
Libre Office is, if you avoid complex features, mostly compatible with Microsoft Word, Excel and Powerpoint
Optical Media Burning Software (CD/DVD/Bluray)
CD Burner XP allows you to save data to recordable CD, DVD & Bluray discs
Picasa catalogues images with an easy to use interface that allows photo editing and sharing. Many believe you have a copy in Picasa and a copy on your disk don’t delete the one in Picasa there is only ONE copy.