There are performance tests like UserBenchmark and PassMark.
Maybe try monitoring software
https://windowsreport.com/hardware-diagnostic-tools-windows-10/ to see if RAM or PSU is dropping out.
A cleanup and defrag (use only on platter drives) might speed things up in general.
Looks like Vista supports system file checking:
https://neosmart.net/wiki/sfc/ to find OS errors.
It could be as simple as a loose connector if the case has been opened up. Be gentle. One at a time.