How to Check for Bad Sectors: Testing an Internal HDD for External Storage

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Converting an old internal hard drive into a portable external one is a brilliant way to recycle hardware, but it comes with a major "if"—if the drive is actually healthy. Before you trust an old laptop HDD with your precious photos or documents, you must verify its physical integrity.

A drive that "works" might still have hidden bad sectors—physical damage on the disk surface that causes file corruption or sudden hardware failure. This guide shows you how to use professional-grade diagnostic tools to ensure your repurposed storage won't let you down.

Quick Steps: How to Check HDD Health

To ensure an internal hard drive is safe to use as external storage, follow these two diagnostic steps:

1. Scan for Bad Sectors (Windows CHKDSK)

1. Connect the HDD to your PC via SATA-to-USB.
2. Open Command Prompt (Admin).
3. Type chkdsk X: /r (Replace X with your drive letter) and press Enter.
4. Check the results: 0 KB in bad sectors means the drive is healthy.

2. Run a S.M.A.R.T. Diagnostic

1. Download and launch CrystalDiskInfo.
2. Locate your drive in the top menu.
3. View the Health Status:
   • Good (Blue): Safe for all data.
   • Caution (Yellow): High risk of failure; store non-essential data only.
   • Bad (Red): Drive is failing; do not use.

How to check internal HDD health for external storage

Testing a Used Internal Hard Drive: A Step-by-Step Health Check Guide

Before using a laptop's 2.5 inch internal hard drive as external storage, we must ensure that the concerned HDDs are free from any bad sectors and read write errors. If the hard drive reports any bad sectors then we won't use it to store important data.

Hard drives with bad sectors can fail any time and over time such a drive will develop more bad sectors. Bad sectors are a clear sign of mechanical wear and an early warning that at some time the drive would definitely fail.

Warning: A hard drive or SSD with bad sectors must not be used to store important data. You also never use such a HDD as your primary backup drive. Eventually, it will fail at some point. Storing important data on such a drive will result in data loss and file corruption beyond recovery. You can use this drive just for storing unimportant data such as movies.

Now, let's move on to check the 2.5 inch hard drive for errors and bad sectors.

How to Use CHKDSK to Check Hard Drive's Health and Identify Bad Sectors

In this section, we're using chkdsk command on Windows 10/11 to check the hard drive's health. Our purpose here is to find out whether the drive we're about to use is reliable to be used as an external storage device.

1. Connect the 2.5 inch internal HDD to your Windows PC by using the SATA to USB cable or enclosure.
2. Make sure the drive is visible in 'My PC' with a label 'External Storage' that we created earlier.
3. Note the drive label for this externally connected internal hard drive. 'F:' is the drive letter in my case.
4. Open command prompt (CMD) with administrator privileges. To do this, type 'CMD' in Windows search box, once you see 'Command Prompt,' right click on it and select 'Run as administrator.'
5. In the command prompt type: chkdsk X: /r. Replace X: with your drive's letter. After correctly typing the command, hit enter and let chkdsk perform a thorough scan of the hard drive.

Running chkdsk /f /r in an elevated Command Prompt to verify disk integrity and repair bad sectors.

6. For a 500 GB hard drive, chkdsk will take about more than an hour to finish the drive scan before returning the results.
7. If chkdsk reports no bad sectors or errors then you can use this drive as an external storage.

I used CHKDSK on my 12-year-old 2.5-inch internal hard disk from Hitachi HGST and it reported 8 KB in bad sectors. This means a very small portion of the disk’s physical surface has become unreadable and has been permanently marked as unusable by the file system.

Scan Result: Review the summary. If "KB in bad sectors" is greater than 0, the drive may be failing.

In practical terms, 8 KB is an extremely small amount of space, but its presence confirms that the drive has started to suffer from physical wear, which is expected at this age. While the operating system will avoid using these damaged sectors, their appearance indicates that the disk is no longer in perfect health and may continue to degrade over time.

The drive may still function for light or non-critical use, but it should not be trusted with important data, and maintaining regular backups—or planning a replacement—is strongly recommended.

How to Find Hard Drive Errors and Early Signs Of Failing Using SMART (S.M.A.R.T) Data

Every internal hard drive or SSD or even external hard drives come with S.M.A.R.T technology. S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology) is a hard drive health monitoring system.

By analysing SMART data we can detect the early warning signs of a hard disk failure. A hard disk won't fail suddenly in many cases, therefore we always have time to transfer data to a new drive.

So, let's see how can we analyze the SMART data for your 2.5 inch internal hard disk to detect read/write errors, bad sectors and early signs of failing.

1. Download and install CrystalDiskInfo. If you don't wish to install it, you can also download the portable .zip package.
2. CrystalDiskInfo is only available for Windows 10/11. If you're using a Mac then you can use Apple's Disk Utility.
3. Make sure to connect your 2.5 inch internal HDD/SSD to your PC/laptop using the SATA to USB cable or enclosure.
4. After downloading CrystalDiskInfo, open it by double clicking DiskInfo64.exe.
5. In CrystalDiskInfo, click the drive with only one partition. You can also check the name of your 2.5 inch HDD in CrystalDiskInfo that'll help you identify it.
6. If CrystalDiskInfo shows no warnings and displays the status as 'Good' then you can use this hard drive/SSD as an external storage device.
7. But if you see any warning or status as 'Caution' then it is an early warning sign of hard drive or SSD failure.

The same Hitachi hard drive now shows a Current Pending Sector Count of 100 in CrystalDiskInfo. This means there are many sectors on the disk that the drive is struggling to read and has not yet been able to repair or permanently mark as bad.

Using CrystalDiskInfo to read S.M.A.R.T. data. A "Caution" status usually indicates reallocated or pending sectors.

Unlike confirmed bad sectors reported by CHKDSK, pending sectors indicate ongoing instability and a much higher risk of sudden data loss. At this level, the drive is clearly in poor health and may degrade quickly with continued use.

While it might still operate for short periods, it should no longer be considered reliable, and replacing the drive is strongly recommended. Therefore, I'm not using this drive for regular backups. I'll use this drive to store only unimportant data.

Conclusion: Trust, but Verify

Reusing old hardware is environmentally friendly and cost-effective, but data loss is a high price to pay for a "free" drive. If your drive passes both the CHKDSK surface scan and the S.M.A.R.T. analysis with a "Good" rating, you can confidently use it as your primary external storage.

However, if you see even a few bad sectors, treat that drive as a ticking time bomb—fine for temporary file transfers, but never for your only copy of important data. When in doubt, the peace of mind offered by a new SSD is always worth the investment.

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About the Author at PCNexus

I specialize in simplifying Android technology for users who find their smartphones overwhelming. With experience dating back to Android Froyo 2.2 (over 10 years in mobile and PC troubleshooting), I solve real-world issues (related to smartphones and PC troubleshooting) on PCNexus using tested, practical fixes that make your devices work for you—not against you.

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