|Upgrade versions require a qualifying product to upgrade from. |
If you buy or build a new computer without a qualifying version of Windows already on it, you may not be able to install Windows 7 on it by using the upgrade family pack. Something to consider.
Not sure if you could provide a restore CD from your Acer desktop and use it as a qualifying product or not. I don't think so though.
Installing a different motherboard in an OEM computer and getting the original OS working is a crap shoot. Generally speaking you have a better chance if the chip set is the same as the old board.
In answer to your quastion about moving the IGP that is not possible because IGP stands for Integrated Graphics Processor. That means built onto the motherboard.
You would need to get another board with an IGP or add in a graphics card.
"He checked that the right voltage is flowing through"
The above does not necessarily mean the power supply is good. If you can borrow a compatible power supply I suggest that may be the issue with your system.