I think I know the answer to this question already but I figured I would pursue all avenues first.
A friend has experienced a hard disk failure, I'm not sure the exact cause of the failure but I believe it is mechanical. They have about half the data backed up but have some important data on the disk they need to recover.
I believe the failure to be mechanical because a new disk has been installed in the machine, the machine boots but the other disk is not detected by the bios. The jumper settings are correct. How can I tell exactly what the issue with the disk is and is there any way of recovering the data without paying for a recovery service?
If the disk is not detected by the bios it is an electronic error, not a hard error (such as a crashed head or failed motor). In such instances, replacing the controller on the drive should be sufficient to recover the data. If identical drives are still available (or one can be acquired) this could be attempted by a competent amateur, otherwise a professional recovery service is the only option.
However, before panicking, it's always worth trying the drive in a USB disk box, you might get lucky.
HDD recovery is only about $500 for a 500 GB drive... how much time can you afford to put towards this? At $100/hour you've got limited time to do the recovery.
If you do have a failed drive and you MUST get the data off, I would not tamper with it at all if you intend to salvage the data.
If you need your data recovered PM me and I'll send you my contact.
I am not affiliated in any way with this company. I only use them because they get the job done quick and won't charge you if it can't be recovered. I have several clients that run HDD intensive applications (industrial automation SCADA nodes) whereby the drives fail every couple of years because of so many writes.
I know you said the failed hd can't be detected by bios, but can you see the drive from with windows under My Computer. this is assuming you're new drive is set to master and you're old damaged disk is slave. Another unlikely, but possible issue may be the ribbon cable you are using. Could it be damaged?
The usb disk enclosure as suggested in a previous post may also be very worth trying.
If the data is critical you may be best seeking professional advice.