Chip creep refers to the problem of a microprocessor (chip) which, over time, would work its way out of the socket; this was mainly an issue in early PCs.
Chip creep occurs due to thermal expansion; the contracting and expanding during system heat up and cools down. While chip creep was most common with older memory modules it was a problem with other main chips (or CPUs) that were inserted into CPU sockets.
To fix chip creep, users of older systems would often have to remove the case cover and push the loose chip back into the CPU socket. Today's computer systems are not affected so much by chip creep since chips are mainly soldered into place or are more securely held by various types of retainer clips and system cooling has improved.
Power supply units, processor and system computer fans nowadays (like most electronics) are much more reliable. This is due to many things but often the fans used to keep components cooled are speed controlled so a hot PC will have the fans running at full speed and a cooler PC will have the fans running slower with many benefits, power saving, a reduction in noise whilst allowing much better efficiency and stability.