What Is the Active Partition?
The active partition is the primary partition on a hard disk that contains the boot loader or start up files. When your computer turns on, the BIOS or UEFI firmware looks for this partition to start the operating system.
Key Characteristics-
- Must Be a Primary Partition: On a basic MBR (Master Boot Record) disk, only primary partitions can be set as active.
- Contains Boot Files: For Windows, this includes files like
bootmgr(Boot Manager) and the Boot Configuration Data (BCD). - Only One Active Partition per Disk: On a basic MBR disk, only one partition can be marked as active at a time.
- Not Required on GPT Disks: With GPT (GUID Partition Table) and UEFI systems, the concept of an active partition is mostly obsolete; they use a separate EFI System Partition (ESP) instead.
How It Works-
- The computer powers on and the BIOS performs the POST (Power-On Self Test).
- The BIOS checks the MBR (first sector of the disk) to find the active partition.
- The boot sector of the active partition is loaded and executed.
- The boot loader launches the operating system.
Active Partition vs. Other Terms
| Term | Description |
|---|---|
| Active Partition | Contains boot files; BIOS loads this to start the OS. |
| System Partition | Contains the files needed to boot Windows (can be the active partition). |
| Boot Partition | Contains the OS files (i.e., the actual Windows directory). |
| Primary Partition | A type of partition that can host an OS and be marked active. |
| Logical Partition | Cannot be marked active; part of extended partitions. |
Common Issues-
- “Missing Operating System” Error: Can occur if the wrong partition is marked active or if the active partition is damaged.
- Fixing It: Use tools like Disk Management, DISKPART, or a Windows recovery environment to change or repair the active partition.