Stuffing a harddrive installed with win7+games in a completly new PC.?

You can move a HD to new hardware and if it won't start up on it's own:

SysPrep it on the old hardware to remove all drivers, SID, HID, Activation so that it starts up like a new install but with all Programs, settings and files intact. SysPrep to move HD to another computer

Boot Paragon Adaptive Restore CD on the new hardware and point it's P2P Adjustment feature at the Win7 partition on the moved HD. It does the same as SysPrep but on the new hardware.

You can also capture an image with Acronis True Image with Universal Restore and reimage to the new hardware choosing the option for Univ. Restore during reimaging.

gregrocker pretty much said it all. With his advice it should be possible to make the change.