Windows Vista build 6001.18000 is Service Pack 1 of the Windows Vista operating system developed by Microsoft. It was made available to MSDN subscribers on 2008-02-15, and released to the Microsoft Download Center and Windows Update on 2008-03-18. Service Pack 1 addressed many user complaints by improving the overall performance and stability of the operating system,. New features include Bitlocker Drive Encryption support on multiple partitions, support for the exFAT file system, and DirectX 10.1.