It's said that Windows Vista is nearing the first release candidate.
The last widespread public release of the OS was Beta 2, which while functionally complete, still contained many annoying issues for testers, especially with third-party software. Beta 2 was based on Build 5259, but the operating system has come a long way since then. Two Community Technology Preview builds were released to users in the CTP program: the December CTP (5270) and the February CTP (5308/5342). Nick White, the Microsoft product manager who announced the news about RC1, says that he is personally using Build 5505, which is a newer one than RC1 will be using. Build numbers are ostensibly a record of how many times the operating system has been fully compiled, although sometimes they will make major numerical jumps for significant releases.