Microsoft’s next operating system, Windows 7, has finally entered RTM (Release to Manufacturers) stage. But don’t expect the Arabic version until October.
Also remember that if you did purchase a qualified Vista machine then you might be eligible for a free (or cheap) upgrade option to Windows 7, and this will be valid in Saudi Arabia as well.
If you hope to have a dual language setup with Arabic and English then your only legal option is buy Windows 7 Ultimate Edition ($330). This has been the same since Windows Vista and Microsoft has no intent of allowing a dual language license for Saudi Arabia and the rest of the Arab World.