How can I keep a hard drive cool in an airflow-limited Lenovo ThinkCentre?

The simplest fix is to use a SATA SSD instead of a mechanical hard drive. It will run much cooler, use less power, and be faster. A 2.5-inch SSD doesn’t need a dedicated bay as long as the SATA and power cables reach it; you can use a 2.5-to-3.5-inch adapter, or secure it somewhere solid with suitable mounting tape or brackets. Don’t leave it loose inside the case.

Since this is a ThinkCentre M57p, the compact OEM layout may simply have very limited airflow around the storage area. Check that the CPU and case vents are clean and that the existing fan is actually spinning. If the drive remains over about 50°C even with the panel off and a fan blowing over it, replacing it with an SSD is probably the most practical long-term solution.

Power could be worth checking, but two drives overheating in the same computer points more strongly to poor ventilation or the drive being mounted directly in a warm area. Check the PSU’s SATA power connector and try another connector if available. A failing PSU can cause instability or drive errors, but it normally won’t make a healthy HDD consistently run hot by itself.

Try running the PC temporarily with the side panel removed and monitor the drive temperature. If it stays much cooler, airflow is definitely the main problem. You could also connect a small, quiet fan to one of the motherboard headers and secure it safely so it blows across the drive, even if the case has no official fan mount. Keep the fan and cables away from moving parts.