Most Charitable organizations will take OLD PC equipment the spec may vary but generally a Dual Core amount of memory 1GB a 120GB hard drive will attract attention.
Strip the PC and separate it into its Steel and other metal components and recycle it!
The 'Gold items' are gold plated.....
The operating system can be recovered from the disk and moved on to another PC. Xp home being replaced with XP pro, recover the old operating system, complete with the Certificate of Authentication and transfer it to a new system. The same with windows 7, Windows Vista? I would not bother!
Where we are in Wiltshire
Spring is arriving A new year starts