Scott Mueller's Upgrading and Repairing PCs Forum

Internal connectors getting loose too soon after I already tightened them (by unplugging and replugging) turned out to be, at least sometimes, due to environmental thermal stress. When my room got too cool, my second hard drive was occasionally unrecognized. Solution: Run for a while even without logging in. Just the power supply, the C: drive, and what comes in between is enough to bring the internal temperature of the box up enough that a reset results in both hard drives being fully operational. No disassembly required.

Thermal cycling can cause connection problems, in which case I normally recommend re-seating all of the connections. Scott.