I just went in to Task Manager on Win 8.1. Not long ago it was as I expect, with a number of pre-selected columns and the facility to add more and remove any not desired.
Amongst other features I used to want to see what was reading and writing to disc, and what was happening to instant and cumulative CPU usage, sorting on those columns. This way I was able to identify what was messing me up in whatever way.
It is now a noddy subset on a "prettier" screen, with a mere four fixed columns showing the rolling instantaneous CPU; RAM; Disk and Network activity.
Totally useless except for being able to end a process .
Or - have I somehow totally cocked something up?