Can a failing secondary HDD slow down a PC even when the OS is on an SSD?

Check the easy possibilities too: replace the SATA data and power cables, try another motherboard SATA port, and look for disk errors in the system logs. A loose cable or failing port can produce repeated errors that make the computer crawl.

Using the disk through a USB adapter or external enclosure may keep some drive activity from affecting the system as severely, though opening folders on it can still lag. It’s only a workaround, not a fix—the drive should still be replaced and any valuable files backed up.

Eleven pending sectors are a warning sign, so copy anything important to another drive immediately and check the drive’s SMART health data. Don’t treat this HDD as reliable storage. Replacing it is the best solution, especially if the pending-sector count increases or you see more read errors.

Yes. A secondary drive can slow down the whole system if Windows, File Explorer, antivirus, indexing, or another program tries to access it. Read errors can make the drive retry for a long time, causing freezes, delays, slow startup, or trouble mounting the disk.

A disk scan may identify filesystem problems, but avoid using repair tools or formatting before securing your files. A full format destroys the data and can stress a failing drive, while software repairs cannot make physically damaged sectors reliable.