I have a computer which will not used, however, it is about 4-5 years old already,
is it worth to use it to mine BTC?
If yes, how much will I expect to get in 1 month
If you manage to buy some ASIC and attach them to your computer via USB them it might be worth, or not, depending of costs.
Of course mine with any non asic device is not worth today, even for brand new computers made for games