Installing Snow Leopard on Macbook Pro problem

The fine writing on the bottom of this Mac is almost gone but it looks like A1276, if not then A1278. Anyway, I replaced the dead HDD on this MP Model A1276 with a new sealed 500GB Toshiba SATA HDD. In Disk Utility, I select the HDD and click on ERASE but I am getting an error message

Disk Erase Failed with the error:

POSIX reports. The operation couldn't be completed.
Cannot allocate Memory?

Help please?

And you're running Disk Utility from where? Also, the SATA cable on a machine that old should be replaced at the same time.

Whe I power on i hold the C key to boot from the install disk then I open disk utility

OK, you didn't mention how you were running Disk Utility. I gather then, you're using your original or a retail Snow Leopard disk to boot the machine and run DU from it. The SATA cable may be bad. Do you have a hard drive adapter or an external SATA carrier case? If you do, you can try erasing and formatting the new Toshiba drive that way and then install it in the machine. If the drive can't be seen after that, it would mean the cable is bad.

Sorry no, I don't those accessories. BTW, as mentioned the fine writing on the bottom of this unit is faded so I can't see the serial number to try Apple for help, is there any way to get the units serial number via DU or anything else so I can try Apple support for help, maybe send the unit in to them?

Sure, that's easy. Apple menu, About This Mac, More Info. The SN will be listed along with an option for a system report.

It is either a 2009/10/11 model MBP as they all used the same model number, just various changes to the base model. Unclear what operating system you are using but use the OS X.6 system install disc, pop it in the optical drive, reboot and hold down 'C' and then go to Repair Disk and see what is reported.

You do the same to format the Toshiba drive. Format Mac OS Extended (Journaled) run the Installer and update. If using OS X.7 or later go into Recovery mode and do this.