How to Partition a Drive Correctly (Without Losing Your Data)

MBR versus GPT, a layout that survives reinstallations, how to shrink a full system partition, and the rules that keep partitioning from turning into data loss.

Partitioning scares people because the tools delete things without asking twice. In practice a good layout is decided once and left alone for years, and most changes you will ever need, such as shrinking a full system partition or moving games to another drive, can be done without touching the data itself.

MBR or GPT

Modern machines should use GPT with UEFI boot. GPT handles disks larger than two terabytes, keeps a backup copy of the partition table, and is required for Secure Boot. MBR survives on machines upgraded from much older Windows and on some legacy boards; if your disk uses it and your firmware supports UEFI, converting is worth doing during a reinstall rather than in place. Windows also creates two small hidden partitions at setup: an EFI system partition of roughly 100 to 500 megabytes and a recovery partition.

A layout that ages well

• System partition: 200 to 300 GB on an SSD, enough for Windows, applications and a comfortable margin.
• Data partition: everything else on that drive, for documents, projects and media that should survive a reinstall.
• Page file and temporary files: on the system drive unless it is tiny, since a separate drive beats a separate partition on the same disk.
• Games: a second physical drive if you have one, because modern titles take a hundred gigabytes each.
• Backups: never on the same physical disk, no matter how many partitions you carve out of it.

Shrinking a full system partition

1. Back up anything irreplaceable first and create a restore point.
2. Clear temporary files and reduce the page file, which often blocks the shrink far earlier than free space suggests.
3. Open Disk Management, right-click the volume and choose shrink. The wizard reports how much can genuinely be freed.
4. If the available size is far smaller than expected, a system file is in the way: disable hibernation, defragment or trim the drive, then retry.
5. For stubborn cases use a third-party partitioning tool that can move files aside during a reboot.
6. Create a new partition in the freed space and format it as NTFS.

Extending and merging

Extending a partition only works into adjacent free space on the right side, which is why deleting a partition in the middle of a disk rarely frees anything useful. Merging two partitions means moving data, so back it up rather than trusting a warning dialog. Windows can extend a partition sitting at the end of a disk on its own; anything more involved needs a dedicated utility and a plan for the moment the machine loses power halfway through.

Rules that keep you safe

• Make layout changes from a running Windows, not from a rescue environment, unless you have no alternative.
• Resize a data partition rather than the one you are booted from whenever possible.
• Leave ten to fifteen percent of an SSD unallocated, which the controller uses for wear levelling.
• Do not hide a second operating system on an unlabelled partition and expect it to survive updates.

One rule covers all of this: assume the operation will fail and plan for the version where it does. A current backup on a different physical disk turns a catastrophe into an irritation. If something goes wrong and data disappears, stop writing to that disk immediately, because recovery tools can find deleted files but never overwritten ones.