If you install a new hard drive and install an Operating System on it and it suddenly acts like it is not there, it may be a loose connection.
If a bootable CD, such a s Knoppix, is not able to read your hard drive, it can have several causes. The list of possibilities below can also be used for troubleshooting hard drives, floppy drives, and CD/DVD drives.
CAUTION: Make sure the power is off and that the PC is disconnected from power. Also be sure to avoid static electricity, or you will need a new PC. Do not force any thing. All parts should easily fit together if they are properly aligned. Sometimes you may have to push or pull harder than you think. Just be careful to make sure any levers or buttons that hold it in place are not overlooked.
* Least likely is that a new hard drive has failed. Try the other options before assuming it is the new hard drive. If all of the below do not work, and it is a new hard drive, contact the manufacturer. New hard drives should include very good instructions for installation and troubleshooting. When in doubt read the instructions.
* Open the case and make sure that all the connections are correct.
* Unplug the power supply connection, make sure there are no bent pins, and plug it in securely.
* Repeat the procedure with the connection to the motherboard, make sure no pins are bent.
* If you have multiple drives, try hooking up just one drive to make sure you can read it.
* Make sure that the power supply, and other components are working correctly. It is possible that another component of the PC has failed.
* If you have another PC available, try connecting it to the other PC. This could point to failure of the power and/or motherboard cables in the original PC.
* If none of the above works, call in professional help. You can also beg a friend or family member to help. If you cannot pay a friend or family member, a good meal, is a nice way to get them to rescue you again.