Windows XP SP2 32-bit or Windows Vista 32-bit, 512 MB or more RAM, 350 MB hard disk space, DVD-ROM drive. You must be running at least Windows XP Service Pack 2 to install and run Sibelius 6. If you have Windows 95, Windows 98, Windows Me, Windows 2000 or Windows NT 4.x, you need to purchase an upgrade to a more recent version of the Windows operating system. Additional requirements for using Sibelius Sounds Essentials and Kontakt Player 2, especially for scores with many instruments. Mac OS X 10.4.9 or later, or Mac OS X 10.5, 512 MB+ RAM, 350 MB hard disk space, DVD-ROM drive. Sibelius is a Universal application, which means that it runs on both older Macs with PowerPC processors and new Macs with Intel processors.