Let's say my opponent has a probe droid (3) with Targeting Computer (1) on it.

If I kill it, do I get 3 or 4 points?

Points are scored for the attachment as well. 3 for the Probe Droid, and 1 for the attachment.

"Skirmish Attachments", RtH Page 5:

When a group with an “Attachment” card is defeated, the opposing player scores VPs equal to the deployment cost of the “Attachment” card, in addition to the VPs he scores from the defeated group’s Deployment card.

"Skirmish Attachments" rules from insert:

When a group with an attachment card is defeated, the opposing player scores VP equal to the deployment cost of the attachment card in addition to the VPs he scores from the defeated group's deployment card.

Edit: Ninja'd

Ninja'd with formatting.

But you can't score the points of a non-attachment upgrade, right?

But you can't score the points of a non-attachment upgrade, right?

Correct. This only applies to skirmish attachments.

Is it possible to make the game unwinnable with sufficient unattached upgrades? (assuming a theoretical number of them up to the total list)

Is it possible to make the game unwinnable with sufficient unattached upgrades? (assuming a theoretical number of them up to the total list)

Not really, because wiping out the other side always counts as a victory.

Is it possible to make the game unwinnable with sufficient unattached upgrades? (assuming a theoretical number of them up to the total list)

Not really, because wiping out the other side always counts as a victory.

What if the list doesn't have any figures? Hypothetically, all the points are spent on unattached upgrades. Your army couldn't take any damage.

We shouldn't entertain impossible hypothetical scenarios.

If you have no figures left aren't you considered defeated? (Am I wrong?) So even if you're able to complete the set-up steps as soon as the game begins you have no remaining figures and instantly lose.