Adding an SSD is the best value upgrade for an old, slow PC, but reinstalling Windows, your apps, and your files is a pain. "Disk cloning" moves your entire system, apps, and settings to the new drive bit for bit, so the PC boots exactly as before. This guide walks you through it.

1, Prepare first, do not skip

Back up. Cloning carries risk, so copy important files somewhere else before you start. Cloning is not a backup, do not confuse the two.

New drive capacity should be at least the used space on the old system. The new drive can be smaller than the old one as long as it is not smaller than the used space. If it is larger, the extra space can be merged into C later, in Split, Extend, and Merge Disk Partitions on Windows, Including Growing C.

Decrypt or suspend BitLocker first. If the old drive is BitLocker-encrypted, suspend or fully decrypt it, per How to Enable BitLocker on Windows and Back Up the Recovery Key, or the clone may fail to boot or keep asking for the recovery key.

Connection. Laptops commonly use USB to SATA (2.5 inch) or USB to NVMe (M.2) enclosures or cables. Desktops can use a second bay or slot directly.

2, Pick among three cloning approaches

Approach 1, full-disk clone, moves system and data together. Best when "replace the old drive, lose nothing". Tools: AOMEI Partition Assistant "Clone Disk", DiskGenius, Macrium Reflect Free, or Samsung Data Migration (Samsung SSDs only).

Intelligent clone (recommended) copies only used sectors, works across different sizes and is fast. Sector-by-sector clone copies byte for byte, slow but most faithful, only needed when both drives are identical.

Approach 2, system migration only. Best when "new drive holds the OS, old drive becomes data". AOMEI Partition Assistant has a dedicated "Migrate OS to SSD" that moves only the system and boot partitions.

Approach 3, image then restore (advanced). Use Macrium to image the old drive, then restore to the new one, or capture a WIM with DISM. Flexible but command-line heavy, beginners should pick approach 1 or 2.

3, Key settings that decide success

4K alignment. In the clone tool, tick "4K alignment, SSD optimization". Without it, SSD performance and life suffer. Most tools tick it by default.

Clone the EFI boot partition too. Otherwise the new drive will not boot and shows a black screen. A full clone carries it automatically; with system migration, confirm the tool also copies the EFI System Partition.

Keep GPT and MBR consistent. Match the new drive's partition table to the old (UEFI machines are usually GPT) and let the tool handle it.

Do not swap source and target. In the clone UI, "source" is the old drive, "target" is the new one. Swapping wipes the old drive.

4, After the clone

Power off, remove the old drive, or set the new drive as first boot in a desktop. Enter BIOS or UEFI and set the new drive first (Del, F2, or F12 at startup, keys vary). If it will not boot, work through the boot-failure guide.

Once in Windows, verify everything works, apps open and files are there, before formatting the old drive as storage. Do not rush the format.

Extend C. When the new drive is larger, merge the unallocated space into C, in Split, Extend, and Merge Disk Partitions on Windows, Including Growing C.

Run SSD optimization, enable TRIM and disable defrag, in SSD Optimization and Hard Drive Health (SMART) Check on Windows.

5, Common risks and fixes

Clone interrupted: just redo it, reselect the target, leave the source alone.

New drive will not boot: usually the EFI partition was not cloned, or the BIOS boot mode (UEFI, Legacy) is wrong, adjust in BIOS or rebuild the boot.

Activation lost: the digital license is tied to the motherboard, swapping a drive in the same machine usually keeps it.

Slower boot: check 4K alignment and whether the old drive is still set first in BIOS.

Clone or reinstall, which to pick

Cloning wins on effort: the system, apps, activation, and personalization all move over, ideal when you just want the old machine to feel faster. A clean reinstall wins on cleanliness: it sheds bundled junk and accumulated cruft, ideal when the old system is already too messy to save. If the current system is merely slow, clone first as a safety net, then decide whether a reinstall is worth it.

Single-bay laptops

A laptop with only one drive bay cannot hold both drives at once. Clone to the new drive using an external enclosure first, confirm it boots, then swap it in. The old drive becomes a handy external disk in the same enclosure, do not toss it.

If the new drive is NVMe and the old one was SATA, confirm the BIOS boot mode is UEFI, not Legacy, or the clone will not boot. A cloned drive keeps the old computer name and activation, so do not run two identical clones on the same network at once, or you will hit name conflicts.

A few practical notes

Keep the old drive safe for a few weeks after the move. If you discover missing data, the original is still intact and readable, so do not wipe it in a hurry. Label the clone clearly so you never boot the wrong disk by accident.

Watch the partition style. If the old disk was MBR and the new one is GPT, or vice versa, the clone tool should handle the conversion, but confirm the target boots in the correct mode. A mismatch between disk style and firmware mode is the most common reason a cloned drive fails to start, and it is far easier to fix before you remove the old drive.

Summary

The safest path to a new SSD is: back up, decrypt BitLocker, intelligent full clone with AOMEI Partition Assistant or DiskGenius (tick 4K alignment), swap and set the new drive first, verify then format the old one, extend C and optimize the SSD. No reinstall, done in half an hour, and the old machine flies.