Is there anything like Reliability and Performance Monitor for WinXP out there?
Anything that is actually worth using?
Anvir Task Manager Free works with Windows XP
It gives you detailed information about every process that is running, and about applications running automatically on Windows startup including all hidden applications.
A portable version is available.
Moo0 SystemMonitor lets you keep your eye on system resource usages of your PC. It currently supports 36 kinds of information including CPU, Memory, Network, and detailed HDD usages. Using this software, you may discover what is limiting your system performance in each occasion.
Moo0 SystemMonitor is freeware, a portable version is available.