After power supply change hard disk light is always on

Can you elaborate a little? Does the PC boot into windows? Does the light shut off when you power off?

Can you elaborate a little? Does the PC boot into windows?
yes, xp with 3 hard discs. and all is perfect.
Does the light shut off when you power off?
yes, and there are not additional evidence of "extra" hard disk activity, all function normal, idle time all well, is very strange... or may be there is hide hard disk activity...?
thank you for your support...

It sounds like your hard drive is just working. You can look at the task manager to see what process are using CPU resources.

all function normal, NOTHING ABNORMAL AT TASK MANAGER...THERE ARE NOT ADDITIONAL CONSUMING CPU RESOURCES. MAY BE THE MOBO. PATH TO HD LIGHT IS DAMAGED OR THE HD LIGHT OR SOMETHING WAS DAMAGED BY THE LATER POWER SUPPLY...