Hard drive

[trini49]

my system crashed and I tried the restoration CD but it is not recognizing the hard drive,so I replaced it and it is still doing the same

 

[house70]

Make sure the cables are properly inserted in the HDD and the mobo.
Try to use a different bootable CD/DVD in your system. If that one recognizes the HDD, it should be good. There are various HDD utilities out there that come as bootable media. I use Killdisk usually, but other formatting or partitioning tools are available, as well.
You can use one of them to low-level format the HDD and only then try to install the OS.
If still no dice, your mobo may be at fault, not the HDD. Let us know.

 

[trini49]

I downloaded Killdisk onto a usb flash drive but it is not reading that either

 

[house70]

You need to create a bootable CD with Killdisk or something similar and boot off that, then see if the program itself (Killdisk in this example) sees the HDD in the menu.
If nothing reads the HDD, there is a problem with the connection between the HDD and the rest of the system. That can be caused by a bad cable (the easiest to check and replace, meaning either the data cable or the power cable), a bad controller on the mobo or bad power supply TO the HDD (something went wrong with the power cable from the PSU to the HDD or with that power line from the PSU to the HDD, meaning something inside the PSU that powers that rail is out).
I would begin the troubleshooting by making sure the HDD receives enough power via it's cable (use a multimeter or use a different rail to power the HDD from the PSU). Then, I would ensure the data cable (from HDD to mobo) is in working order (replace it with another one). Finally, if neither works, I would blame the controller chip on the HDD and move to replace the HDD (unfortunately, the mobo is integrated enough, meaning that users can not replace individual components on them).
Let us know, good luck.