After installing a second hard drive in my Mac when the computer boots up it searches for the operating system on this second hard drive (which is blank) rather than the other drive in the machine which contains the OS (in particular, MacOS 9.1). Running MacOS 8 and 8.1 have not fixed the problem. The Apple dealer advised starting up with the OS 9.1 disk and then selecting the startup disk. There is no start-up disk choice available! Can you advise?

When using the MacOS 9.1 CD to boot the computer, in order to change the startup disk, be aware that the option to select the disk will not appear automatically, so you will have to use the control panel. If you have not tried this already, in the Finder go to the Apple menu > Control Panels > Startup Disk. From this control panel, you should be able to change the startup disk. However, if you cannot find this control panel, it may be that this particular control panel does not load when booting from the CD. Unfortunately, I cannot offer any further advice as I am not particularly knowledgeable on Macintoshes. So, if there are any Mac readers out there with a suggestion for Rex, please write in with your suggestions.