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Windows 7: Can't mark OS partition as Active


13 Nov 2010   #1
Pericles

Windows 7 Home Premium
 
 
Can't mark OS partition as Active

Greetings,

After formatting my new laptop, I deleted the manufacturer recovery partition, the 100MB partition, resized, merged, created a new Data partition, etc. However, I cannot mark my OS partition (C as Active; I can only make my Data (D partition Active. Please advise.




Attached Thumbnails
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My System SpecsSystem Spec
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13 Nov 2010   #2
Kari

Microsoft Community Contributor Award Recipient

Windows 8.1 Pro with Media Center
 
 

I'm confused; your screenshot clearly shows partition C: being active.
My System SpecsSystem Spec
13 Nov 2010   #3
Orbital Shark

 
 

Hi,

Setting an Active partition is used when you have multiple OS's installed and wish the system to 'Default' to a particular OS when booting up.

I've seen occasions where setting the only OS partition to active can mess up the MBR and a repair is required which resets it back to it's default state to allow booting.

update: It looks as if the 'Active' partition is the first in the string (the string starting from left to right) of partitions from the same disk.


OS
My System SpecsSystem Spec
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13 Nov 2010   #4
Bare Foot Kid
Microsoft MVP

W 7 64-bit Ultimate
 
 

Hello Pericles.



There can only be a single active partition per Hard Disk Drive (HDD) as that's the flag that tells WinRE (Windows Recovery Environment) where to repair startup errors or where to create new boot files; do not mark D: as active, it will cause the OS not to boot; have a look at this tutorial at the link below for more info.

Startup Repair - Run 3 Separate Times
My System SpecsSystem Spec
13 Nov 2010   #5
pip22

 

Orbital Shark said "Setting an Active partition is used when you have multiple OS's installed and wish the system to 'Default' to a particular OS when booting up"

Having a partition marked "Active" is not just used for dual-boot configurations. Regular, single installations require an active partition too.
My System SpecsSystem Spec
13 Nov 2010   #6
mjf

Windows 7x64 Home Premium SP1
 
 

Quote   Quote: Originally Posted by Pericles View Post
Greetings,

After formatting my new laptop, I deleted the manufacturer recovery partition, the 100MB partition, resized, merged, created a new Data partition, etc. However, I cannot mark my OS partition (C as Active; I can only make my Data (D partition Active. Please advise.
Did you make recovery disks before doing this?
As stated your OS partition is already active. Assuming your OS is ok then the Bare Foot Kid advice is your next step.

Just curious - why did you do this?
My System SpecsSystem Spec
13 Nov 2010   #7
whs
Microsoft MVP

Vista, Windows7, Mint Mate, Zorin, Windows 8
 
 

It looks to me as if you deleted your MBR when you deleted the 100MB partition and now you cannot boot. The fix is as Bare Foot Kid says. Marking a partition active without a MBR on that partition will do nothing for you.
My System SpecsSystem Spec
13 Nov 2010   #8
mjf

Windows 7x64 Home Premium SP1
 
 

In your case follow the tutorial carefully. You will almost certainly need 3 repairs assuming your OS is still in tact.
Your MBR on the first sector of the HDD will need it's partition table updated which includes marking the new active partition entry. (One repair)
Your PBR (partition boot record), boot manager and BCD store used to be part of your 100MB partition. They now need to be in c: requiring the 2 extra repairs.
Hopefully then Windows will load.
My System SpecsSystem Spec
13 Nov 2010   #9
Pericles

Windows 7 Home Premium
 
 

My computer boots perfectly fine as is. Is there any reason to do all this? I only use a single OS.
My System SpecsSystem Spec
13 Nov 2010   #10
whs
Microsoft MVP

Vista, Windows7, Mint Mate, Zorin, Windows 8
 
 

Quote   Quote: Originally Posted by Pericles View Post
My computer boots perfectly fine as is. Is there any reason to do all this? I only use a single OS.
Now I am confused. In your disk management picture, C is marked as active. And if it boots, what seems to be the problem? We thought you had a boot problem.
My System SpecsSystem Spec
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 Can't mark OS partition as Active




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