Change hard disks? You may want to ask in the forum that matches your OS.
In closing the cleaners seem to not cure your issue for Windows XP and Vista. Registry cleaners did work on the old Windows 98 machines and days.
im having troubles since i uninstall some of my apps, then when i checked my system registry bunch of junks were left behind by the apps i already uninstall. is there any way i could clean my registry aside from expensive registry cleaners. my computer suffers from crash and slow start up. please give me advice so i can clear up my registry from junks. thanks for those who will reply.