Just remember that although you can update to 9901, you can't update to the next release from 9901. For those who updated to the leaked 9901 you will have to reinstall when the next release is done in January. Microsoft will not fix this since 9901 isn't part of the preview programme and only available through unofficial means.
Agreed, you can make an update from ANY build so long you have the ISO. Only the built in Upgrading mechanism, i.e auto-downloading the next build, is broke in 9901. No big deal... What is a big deal is the fact that my computer name at my Microsoft account has been removed from my account. Now if I try a new install and sign in it no longer shows me my PC. I had several listed, one for my desktop, one for the laptop and one for a VMware install. Since I did not create a new machine name during the install I believe all three have been wiped from existence? So does this mean when the next "Official Build" hits I better do a build upgrade (not a full fresh install) or all my settings/apps in my Microsoft account will be wiped permanently?
Only the automatic downloading and installing of updates is broken, you can still upgrade using an ISO. There will be ISOs, but no official word yet on whether or not those ISOs will be released at the same time as the automatic upgrade. Good point, no idea...
If someone were to update 9879 to the new 'official' build, they could build an "unofficial official" iso and torrent it.
On a master boot record layout yes, since Windows can only boot from active primary partitions, not from extended partition logical drives. On a GUID partition table, the limit for possible partitions is much bigger per above. and even so, you can still VHDboot or WIMboot unlimited number of systems, provided that you have space, or; use the boot device solely as a thin client, booting any available system from the network, if configured Windows cannot boot from MBR extended logical drives. Even though you can create such an amount of logical data partitions, you have much less free root drive letters to assign, requiring you to use folder mount points to make use of them for data. Though in the case of GPT and EFI boot that doesn't really matter, as not letters are used in boot loaders, but volume identifiers (ARC convention or device map) on unassigned partitions.
Above all the logical points made by people here. Who has been able to install more than four Operating Systems in a computer?
I have 6 (W7 & W8.1) OSs installed on Main PC on 3 Hdd. They will all boot when selected - MBR Test Rig 1 has 8 OSs on it, all boot also. Test Rig 2 has 5 OSs incl XP, they all boot too.
For the reason I haven't been able to partition a particular HDD into more than four places for booting OS or primary partitions.
What is the highest number of partitions have you been able to create on single HDD? Despite you succeeded with five on GPT partitions.