My first IT job was in a mixed-bag environment, ranging from Windows 98 to Windows XP. I was so glad to see 98 and ME vanish though — because that meant all the machines would have an easily-accessible Task Manager.
For the uninitiated, Task Manager shows in detail what's going on "under the hood" in your pc. If your pc is suddenly terribly slow, Task Manager can reveal that your memory is all used up, and can show what is using it. Or, it can point out a particular process that has your CPU (brain chip) held hostage. Or it can reveal a virus.
Plus, it normally can let you kill the bad process.
As I alluded, I use the Task Manager all the time in my job. I'm so glad that all current pc operating systems have it.
For the geekily-inclined, here are five enhanced alternatives to the Task Manager that natively comes with Windows.