Which Problem Management metrics do you use?
One of the metrics I use is the average number of incidents in a year for each PC. This can be calculated by deviding the total number of incidents in a month ( x 12) or year by the number of desktops/laptops. When calculated over a longer period of time, the graph will show -hopefully that incidents per PC is falling. Due to Problem Management ofcourse!
This rate may also be used to compare it to benchmarks from Gartner or others. (However I do not have acces yet to this iformation myself.)