While it's preferred that you note down all available hardware via the Device Manager and download the latest drivers for each hardware and reinstall them from either the downloads or the Install/Driver CDs, you can backup your existing drivers by using programs such as WinDriver. Learn more here, I think they even have a freeware version that backs up drivers to a CAB/ZIP file that you can use to restore your drivers after reinstall, in case things go wrong. Learn more here:
*www.zhangduo.com/driverbackup.html