>I have a NT 4.0 OS runing on a single Pentium II machine, but the motherboard accept a second one.
>If I install the second procesor, I have to install the OS again? Or it detect the new configuration?
>If somebody knows... I will be grateful
>

You must do a partial reinstallation, since the SMP support needed to make use of the second chip requires a different kernel (specifically, the HAL changes when multiprocessor support is added.) You won't lose your registry, but you will have to reapply any SPs and hotfixes after the partial reinstall to replace the HAL.

>Thanks
>
>Pedro