Jonathan King has said in a thread.."Marking a partition as active on a basic disk means that the computer will use the loader (an operating system tool) on that partition to start the operating system."
I have a dual XP/Win 7 system which shows:-
Disk 0
(C
Healthy, (Boot Page File Crash Dump Primary Partition) This has my Win 7
Boot (D
Healthy (System Active Primary Partition) This has the XP
Now i can choose which I can boot from and the C does not mention 'Active'.
Can anyone elucidate please? Thanks
PS I am trying to understand this as I am actually trying to delete the XP partition.
The "loader" as you call it is actually referred to as Boot Manager.
In the days of XP, Boot Manager was installed into the same C-partition as the XP operating system itself. All in the one partition... which was necessarily marked "active", in order for the BIOS to know where to go on the hard drive in order to find Boot Manager to start the boot process.
Now Boot Manager reads the "boot menu" found in that same "active" partition, in order to present the list of bootable OS's for you to pick from. If you had only one bootable OS (as you did originally when you had XP only), Boot Manager is smart enough to just default to the one-and-only OS on the "boot menu" and not bother you to manually pick it. There was only one, so it just picks it for you.
Then, you added a second bootable OS when you installed Win7. The Win7 installer discovers that you already have an existing Windows (i.e. XP), and that there already is an "active" partition (i.e. the same partition that both XP and XP's Boot Manager live in).
So first, the Win7 installer replaces XP's Boot Manager on that partition with the Win7 version of Boot Manager. The it adds the location of the new second Win7 OS (which is installed in a second partition on the drive) to the boot menu. Since there are now two bootable Windows systems, Boot Manager will now present the list for you to choose from when you boot the machine.
So, because you UPGRADED your existing one-Windows XP environment to a two-Windows XP+7 environment, you have a boot menu that has two items on it. And the "active" partition (where both Win7's Boot Manager and the updated boot menu live) is still that same partition where XP also lives.
If you pick XP to boot, that partition becomes C... for XP. And the second partition where Win7 lives will thus be lettered as D, from XP's perspective. If you pick 7 to boot, then that second partition will also become C... from 7's perspective... and the other partition (i.e. the "active" partition where XP and Boot Manager live) will then be lettered as D, from the perspective of 7.
The booted OS partition is always C. Other partitions then would be lettered starting at D.
Note: on a brand new empty drive, if you installed just Win7 from scratch and there wasn't a pre-existing WinXP system to add to as a second bootable OS, then the Win7 installer will now create a small 100MB "system reserved" partition and mark it active. It gets no drive letter at all, but Boot Manager and the boot menu are placed here.
Then, the installer creates a second partition where it places the real Win7 system, and points to it in the boot menu located in that small first, active "system reserved" partition. When you boot the BIOS goes to the "active" partition (i.e. the small 100MB "system reserved" partition where Win7's Boot Manager and boot menu live) and discovers that you only have one bootable OS. Again, it just shortcuts things for you and selects that one-and-only OS as if you'd done it, and you boot straight to Win7 which appears on your screen.
Now if you were to add a second bootable Windows (say Win8.1) to your Win7-only environment, that additional Windows sytsem partition where Win7 gets placed would be added to the boot menu in the 100MB "system reserved" partition, and now you would be presented with the list of two bootable Windows systems for you to choose from at boot time... same as when you had XP and Win7.
In other words, in a one OS world Boot Manager simplifies things for you by just going to that one-and-only Windows. If there are two or more bootable Windows systems identified in the boot menu, then Boot Manager presents that list for you to choose from.
And Boot Manager is ALWAYS stored in the "active" partition along with the Boot Menu. In the case of XP, that same partition also holds XP. But for Win7 and newer the OS is placed in a separate partition, with the small "system reserved" partition (that gets no drive letter assigned) housing just Boot Manager and the boot menu.
The booted Windows partition always is lettered as C, no matter which Windows that is. All other partitions are then lettered D, E, etc., from the perspective of whichever Windows (on C, from its own perspective) that you booted to.
Clear? Answer your questions?
