hookturn,
It's highly likely that Speccy and SpeedFan are attempting to read a non-existent sensor input, which is often typical, as "
system temp" normally refers to a motherboard device, where 121°C is completely unrealistic.
As
CountMike suggested, download the "Portable" version of
HWiNFO (Hardware Info). It is frequently updated and trusted for its accuracy, but is sometimes confused with
Hardware Monitor, which is less accurate, is only updated occasionally and is therefore not recommended.
Run HWiNFO using "Sensors Only". It's a very detailed utility, whereas Core Temp is a simple, lightweight utility that's also frequently updated and accurate. AIDA64 is trialware that has a 30 day expiration, which is annoying.
Regardless, I suggest that you disregard "system temp 121°C" and insteads focus on "Core" temperatures, which are your most critical values. "Throttle" temperature for your recent generation i5 is 100°C, but it should not run that hot.
Here's the nominal operating range for Core temperature:
Core temperatures above 85°C are not recommended.
Core temperatures below 80°C are ideal.
Also, keep in mind that Core temperatures increase and decrease with ambient (room) temperature, for which the International Standard (normal) is 22°C or 72°F.
CT