What is the ruling on purchasing a stolen computer from non-Muslim foreign countries, and is it forbidden to benefit from it? And does the one who does so incur the ruling of a thief?

It is not permissible to buy stolen goods or to deal with the aggressor. Whoever does so, while knowing it is stolen, is a partner in the theft. He must return the stolen item to its rightful owner, even through indirect means, without needing to declare it, especially if doing so would result in harm. As for the programs that were run on the device, it is permissible to benefit from them or from what was earned through them, but the benefit of the device that was lost must be compensated and returned along with the device to its owner. This compensation is to be estimated by experts, or by giving what is most likely to clear one's conscience.