Troubleshooting:after repair, system reports incorrect version of OS Error

after repair, system reports incorrect version of OS

Hi,
OK, usual situation, I installed some new software on a Win 7 Pro 64 bit machine (OS patched to date) and, when it rebooted, the computer gave the "No system disc" error message.
Rats,  Never mind, I got the rescue CD that I had generated on the system.
That booted fine, but reported that it was the incorrect version for the system that it had apparently found.
So I tried the self same original Win7 retail install disc but the repair function on that gave the self-same message.

I've grabbed another (identical hard disc, as it happens - even down to being in the same batch) and done a fresh install on that disc, using the same Win7 install disc.
Then shoved the unbootable disc on (using a USB<>SATA cable, as it happens).
 I can
read it fine.
It looks "perfect".
 It has two partitions on, same as the current system disc.
Obviously something has been over-written/altered to make the thing unbootable, but it doesn't appear to have done anything too drastic. 

So, is there any point in copying the small (boot?) partition from the working disc and writing it over the same partition on the non-booting one? Or does "Incorrect version" from the repair disc come as a result of checks to the system partition and not
the boot partitiion? What is actually being checked that can result in the repair software stopping with a "incorrect version" error? 

It's no big deal.
I have a full backup and can restore that.
It's just that, if I come across a similar "incorrect version" message in the future, there may not be a full backup available then.
 I'd quite like to be able to recover this disc, so I know
how to do it in future, should a similar situation arise.
When it may indeed be a big deal.

Any thoughts most appreciated!

Keys to the Problem after repair, system reports incorrect version of OS

Download SmartPCFixer to Fix It (Free)

Make Sure that your Computer Meets the System Requirements

You need to double-check your computer's hardware configuration against the following Microsoft requirements. If your PC hardware is not up to par, then make sure you update where necessary before continuing:

Microsoft Windows Requirements :

• 1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor
• 1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit)
• 16 GB available hard disk space (32-bit) or 20 GB (64-bit)

If your computer meets the minimum requirements above, then continue on…

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