The long and short of this problem is that my computer will not acknowledge the existence of my RA3 disc. I put the disc in the drive, but the computer thinks that the drive is empty, and it cannot see the disc at all. BTW, this is not the Uprising expansion I'm talking about, just to clarify for those who don't find it obvious.
The computer in question is running Windows 7 Home Edition SP1 x64, and its hardware specs are as follows:
2.80 GHz Intel i5 Quad-Core
1GB NVidia GeForce GTS450
DirectX11 is installed and UAC is turned off. All intuitive pieces of advice have been taken before posting this, and none of them work, bear in mind before answering with an obvious suggestion. This version of RA3 is not cracked in any way, and the installation process itself works perfectly on a Dell XPS L502X with an as-near-as-makes-no-difference identical OS.
This has only ever happened to one other title: Supreme Commander Forged Alliance. If this provides any useful information, good.