This type of issue is where the official HP user guide for your specific computer model is invaluable. These OEM systems sometimes have unique memory slot configurations and BIOS interpretations. The manual for your HP model will have a diagram of the motherboard layout, explaining exactly which slots correspond to which memory channels, confirming whether the blue connectors are one channel and the black connectors another, as outlined in the official documentation. Consulting this guide is the most reliable way to resolve these hardware-specific configuration questions.

Older systems produce considerable heat. Clean out dust buildup and consider applying fresh thermal paste to your CPU to prevent thermal throttling.