"Would" entered the English language historically as the past tense of "will", but what was true in Old English (between the 5th and 11th centuries) is no longer true today. Today, "will" is a "modal" verb. Modals do not have a past tense like other verbs. There are some cases where "would" is still used to convey past meaning. One example is "reported speech": "She said she would go swimming tomorrow." Another example is past habitual actions: "Every summer we would spend a week at the beach." Another example (similar to reported speech) is in expressing past intentions: "He hoped he would be a doctor but he didn't pass the exam." In sum, "will" is not a normal verb that has a past tense, but "would" still maintains a few of the abilities that had in Old English to convey a past meaning.

Hi there. Yes it is. But it is also used to express the conditional tense, to show us the consequence of an imagined event or situation. “If they catch me being late for work again, I would lose my job” So on your second sentence, that’s how you are using would. It sounds as if you don’t have money (so it’s an imagined situation), but if you did, you would have got a new computer.

In both of your sentences, "would" is not the simple past tense of "will" but is instead used to express different conditional meanings. Much as I would have liked to, I couldn't accompany him to the concert because I simply didn't have any spare time. In this sentence, "would have" is part of a third conditional construction, referring to a hypothetical situation in the past. The speaker is expressing regret about something they wanted to do but couldn't because of a past condition (lack of time). This shows that "would" is not acting as the past tense of "will" but as part of a hypothetical past. If I had money, I would have changed the computer. Here again, "would have" is used to talk about something that didn't happen in the past. This is a case of the second and third conditionals mixed, as the condition (having money) is in the past, but the action (changing the computer) refers to what would have happened in the past under different circumstances. To summarize: "Would" in these cases is not the past tense of "will" but is instead used to express a conditional situation. "Would have" is commonly used to talk about hypothetical actions or unrealized events in the past, often as part of a conditional sentence.