Programs can lie shamelessly. Look in Hwmonitor (www.cpuid.com/softwares/hwmonitor.html)
and/or in the bios. Well, once the new PSU with the output power should be good, if it is certainly enough to nourish.
Regarding the reboots: Judging by the question you have Windows. In the system settings view included the creation of a dump and you can disable automatic restart. In this case you will see the "Blue screen of death" and there will be the error code. Well, dumps windows dumps to the minidump folder (in folder windows), there are programs that read them and give out the human error codes, which are also cute gugliada in search of a solution.