Dell 8100 Dimension will not find the Hard Drive or CD Rom

If the drives share the same IDE cable, try to replace the cable and make certain it is seated properly on the motherboard. Check for bent pins on either drive and on the motherboard IDE connector. Sometimes pins (especially near either end of the 2 rows of 20 pins) will bend under if they are not lined up with the IDE cable. Also check that nothing changed on the Jumper positions on the drives. They should be set to Master if both drives are single and Master (hard drive) and Slave (CDROM) if they share the same cable.

Hi,
Check to make sure the hard drive jumpers is set to master and the CD/DVD rom is set to slave, have a look at this for an idea >>>>

As soon as you have the jumpers in the right place your system should recognize both drives.



Regards

Did you open the system and change the cable connections?? This happens due to wrong/disturbed cable connections, reconnect it to the proper working slot, if you do not know the right place try all the slots one by one and find the correct position, make sure you connect the power cables too.
Check if the memory chip (Ram) is inserted properly into the slots, Also in the BIOS setup always keep the device detection to "Auto Detect" unless you are pretty sure about the configuration.