Windows Vista/6.0.5000.vbl core.040818-2000
This is among the earliest of the Omega-13 builds. Basically, upon the compilation of these builds, the Longhorn feature set was initially removed, and during the compilation of these builds, Microsoft's main focus at this point was to reimplement the actual Longhorn feature set gradually and over time.
Nothing much is known about this particular build, except that there are several compiles of it, with the build tags vbl_core.040803-2000, vbl_core.040806-2000, vbl_core.040808-2000, vbl_core.040809-2000, vbl_core.040818-2000, vbl_core.040826-2000, vbl_core.040902-2000, winmain.040908-2000, and vbl_core_build(ntbuild).040915-0831, respectively.
Note that the first few compiles may have been compiled before Longhorn entered Omega-13 stage with the code reset, and that this build may have been recompiled for Omega-13 later, judging by the compilation dates.