The summary.
DIAGNOSE THE RIGHT COMPONENT
A machine slow with several programs open needs memory, not a faster processor. When memory runs out the system uses storage instead, and performance collapses disproportionately.
A machine that performs well briefly then slows is thermal — check dust, fans and thermal contact.
Unexplained restarts under load suggest the power supply, which is frequently misdiagnosed because its symptoms resemble everything else.
Unpredictable crashes warrant a memory test.
THE UPGRADE THAT TRANSFORMS AN OLD MACHINE
Replacing a mechanical drive with solid-state. Perceived speed comes from access time, not transfer rate.
WHEN A DRIVE IS FAILING, COPY THE DATA FIRST
Diagnosis can worsen it.
FOR PERIPHERALS, CHECK IN ORDER
Power, then cable by substitution, then input selection, then driver.
The same connector shape may support different speeds, which explains a device working poorly on one port and well on another.
CHECK WHAT THE BOARD SUPPORTS BEFORE ANY UPGRADE
Components are not interchangeable across generations.
