Im surprised how young many of your guys' installs are. i thought i would post this and you guys would blow me out of the water, like usual i did not mean to imply that i reinstall the operating systems on my computers regularly just for kicks. in fact ive never done so. ive always ended up upgrading OSs or computers before that need has arisen. ive just never kept a computer in service quite as long as my faithful ol' inspiron so i was curious. for what its worth, my main rig has only been running its installation of windows 7 since fall of 2010.
I have an old dell laptop with windows 2000 professional and a very old desktop with windows 98 still works but I don't use them.
About 6 months I think. At work about 6 years. I work in IT and there is nothing I hate more than fixing problems with old machines that should just be thrown out rather than resurrected over and over again. It is more common to just reinstall on anything that comes to my desk after someone has left or been given something better. We do still have some Win2K machines that have been gathering dust for years but they are going to have their HDDs wiped this week before getting chucked.
I'm working for one of the big supermarkets at the moment on the distribution side and the IT is ancient! However we use a server based OS that is very new for the distribution business so it'll work on any old piece of crap! Still very frustrating being limited by Windows XP/HDD/Screen Resolution. The latter is particularly irritating because I could do so much more simply with a system capable of higher resolutions. As it stands an upgrade is not economically viable. Same old story of a short term saving lacking the forethought of long term costs!
I still have a couple old laptops running 2000 advanced server... and an even older one running NT4... Oldest in use though is a PowerMac G4 running Leopard which is now 4 generations old....