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AFAIK, the Windows Longhorn builds from 4074 and until 4093 use the same serial, so this serial should work: TCP8W-T8PQJ-WWRRH-QH76C-99FBW
If it doesn't work, maybe it's because that build uses to be very buggy and unstable, so try booting with the 4051 ISO, then insert the 4093 ISO and opean a CMD window. type X:\setup (Where X should be changed to the letter of the CD/DVD drive) and install. Also remember to pre-partition the disk before installing because this build cannot partition disks.
the build 4051 does not want to start the instalation, then I do the same thing with a previous buidl?
I try with the 4074 and the activation key does not work either
For the 4051 issue: Sorry, I forgot which build was the one that boot properly. As for the activation issue: You must set the virtual machine BIOS back to 19/08/04, but most probably you won't be able to set your BIOS back as it will always syncronize with your host. To solve this issue search "How to disable time sync [Name of your hypervisor]" (Hypervisor is like VMWare, VirtualBox, VirtualPC, Hyper-V, etc.).
Note that the Windows betas are well known for allowing installation only in certain amount of time (e.g. from 14/05/2000 until 03/07/2000), that might be why you can't install.