Windows Vista Service Pack 1 (SP1) was released on February 4, 2008 alongside Windows Server 2008 to OEM partners, after a five-month beta test period. The first use of the service pack caused a number of machines to continually reboot, making them unusable. This caused Microsoft to temporarily stop release of the service pack until the problem was resolved. The same release date of the two operating systems showed the merging of the workstation and server kernels back into a single code base for the first time since Windows 2000. MSDN subscribers were able to download SP1 on February 15, 2008. SP1 became available to current Windows Vista users on Windows Update and the Download Center on March 18, 2008. Initially, the service pack only supported 5 languages - English, French, Spanish, German and Japanese. Support for the remaining 31 languages was released on April 14, 2008.