This PC is of the windows XP era - but well specified for that time. It is now running Slackware Linux - a free, well maintained, fast, secure operating system which is running well on this machine. Linux is not troubled by (windows) viruses, so no need to buy anti-virus software. Slackware contains a wide range of software built-in, for example browsers and mail clients for the internet, office software so good for documents and spreadsheets, utilities, games, etc.
Very secure as a multi-user system - users have no access to each other's files, but you can share user accounts if you don't need/want that level of security.
Specifications: 230GB HD, 1GB RAM, Pentium D CPU - 64-bit.
A printed guide is supplied with this to get you started, and I can offer further linux help and tuition, where desired.
It is a big and heavy tower, and I am unable to help with the lifting - bring someone strong!!
For those who have previously had a linux PC from me over the last few years - your operating systems will be due for updating - and in some cases your operating system will no longer support 32-bit. I can offer help in installing 32-bit slackware on your PC - just get in touch.