As far as I know you have to do a complete reinstall because windows does not let you skip a OS in a upgrade. But usually in a upgrade scenario you have to reinstall the applications anyways and transfer files. If all your systems are using the same applications and you bought a Windows 7 key that allows multiple users you can make a custom install disks that install all the updates, applications, and whatever else you choose in the same install with windows. You can use a program called nlite to make the disk and enter all the information so when the disk installs it will not prompt you for anything. You can get a list of other similar tools here: http://www.techradar.com/news/software/operating-systems/10-tools-for-creating-custom-windows-installation-discs-679477. Also depends if your going to keep a 32-bit environment or upgrading to 64-bit because then no matter what you would have to do a reinstall and make sure all your programs work in a 64-bit environment.