On 31 May 2007, all Customer Preview Program (CPP) pre-release versions of Windows Vista will expire. If you are running a pre-release version of Windows Vista (Beta 2, RC1 or RC2), you will begin to receive warning notifications about the upcoming expiration on 18 May. To avoid work disruption and loss of data, we strongly recommend that customers running any of these pre-release versions of Windows Vista migrate their PCs to the final version of Windows Vista prior to 31 May.
Those of you with the CPP still installed will have to plan on what to do next month. Although, I can barely handle using the RTP. People are still using the beta??
Source: Windows Vista Blog