So far, I use Dolphin to del all files in win partition. The use Partition manager to unmount and shrink(600M left). Edit grub to remove winxp. I hope that I did right. Will see when I reboot.
update: it works.Did boot into pclos. Could be that I did not do it the "right way", but the xp is gone and pclos works fine. I my not be that damm after all.