I never reinstall Windows if I can help it. I would much rather track down and fix a problem so I know what caused it in case it ever happens again, or I encounter it on another system. With systems I receive to repair that is another matter because I never know the history of the user's usage of the OS, so I normally just dump the contents of the HDD for a full backup then format and clean install, then copy the user files back so they don't lose anything. It is much easier that trying to fix most user's existing installs because in all honesty most people don't actually seem to use their computers far beyond the default setup... and that raises a big point I've considered for many years..

Most people get a new computer with an OS pre-installed. They don't change it for another OS, and then don't really install much on it other than maybe Office and a couple of games. And all of their personal files normally fit easily onto a 60GB pen drive. This has therefore always raised the question in my mind that for most people a full blown PC with a current spec CPU and loads of ram is complete overkill for most. I know people that when buying a new PC they have to spec the top end CPU, the most ram etc... but then I ask them what they are actually going to be doing on it and they describe email, office, web browsing, some Facebook games and sometimes (but not that often) install a couple of games. Why do these people need a PC with a quad core CPU and 8GB of ram and a full brown GPU? They don't. I have saved quite a few such people a lot of money in the last couple of years... building them a more modest i3 (using its built in GPU) and 4GB ram, with a 60GB SSD. They have been extremely happy with this and it has easily exceeded their needs.

If I worked for PC World I don't think they would be making much money from my sales!