What is wrong with Disk Uility? Why doesn't it work for anything I try to do?

Question

So I have been having a lousy time of upgrading my roommates computer. He has a Mac pro mid 2010 (Ill get the exact model # when he comes back) and he asked me to put in 8 GB's of RAM and a 1TB Hard drive. So I thought it would be an easy task, simply swap out the RAM and HDD, copy everything over to the new HD and he'd be all set. Unfortunatly, Disk Uility seems to fail when I do anything!
Please see these two threads:
How do I fix the Disk Utilities error "Could not Restore, Device Not Configured"?
https://discussions.apple.com/message/20005646#20005646
New Hard Drive is not recognized internally
https://discussions.apple.com/message/20031279#20031279
These are just TWO of the problems that I have encountered while attempting to do what I stated above. After failing at trying to copy over the files, I attempted to install OS X via the startup manager and it worked and I was even able to use the "Startup manager" to boot into it. But his Mac won't recognize it internally!
Even simply attempting to shrink his old HD's partition encounters the error "The disk could not be unmounted" (and I tried with the single partition mounted, and with it unmounted.
I am a windows guy. If he had had a windows computer I would know 1001 tricks for doing exactly this. I even know enough linux to do this on Ubuntu or CENTOS.  But the OS X utilities seem laughable, even worse than the Windows Backup Uility (and I thought that was the worst utility ever!).
So what is the problem here? Is it his whole computer? I am having him return the 1TB HD he purchased to see if that was the cause, but after attempting to shrink his old one and having that fail, I don't know what the heck it could be besides the recovery manager or the computer itself. Disk utility says everything is working great, but I know that can't be right.
Are there some other programs out there that could verify that everything was working ok?  I can't even boot up my own recovery OS's via my flash drive on that Mac.
***Side Note: in the "new hard drive..." thread, Grant tells me that OS X doesn't have a default startup disk after I flash the NVRAM, and that I have to specify one. I think this is wrong because After flashing the NVRAM and having the Mac STILL not recognize the new HD, I was able to put the old one in and boot it without having to specify anything.***

Answer 1

Hi DS,
Thanks for the response. Unfortunatly those documents are of no help to me. I have tried several times to boot into the AHT, which didn't work. And attempting to do an internet recovery won't even allow me to log into my wireless network, even though I know the password is correct.Let us try to go through this step by step, as I've been doing.
1) After resetting the NVRAM it still does not see any new hard drive, and I don't need to select the old HD to boot from it. If it is in it works.
Therefore this means that it is
     a) not the SATA cable
     b) not the new hard drive because my friend got his replacement HD today and I checked them both out. They both work fine on my other friends new macbook pro.
2) The old hard drive can boot up regularly, and the new one can be seen via the SATA to usb connector and booted from, but not via the internal SATA connector.
Also, I still can't boot into Parted Magic, or any other rescue OS I have.
This seems like a very specific problem, and it definatly wasn't anything I did. I followed troubleshooting steps like I normally do and it wasn't a clusterfuck as you so elequently stated.
Please take the time to respond to all of my questions this time, I feel like you are overlooking some very important information.
Thanks,
RFJ3200