The decision is only right when you have an extra PC for work if you have not then I think this is not the best decision. I saw many people who love Bitcoin and want to invest in it to gain profit but with the lack of capital they did not do this, some also fall in that category but they have some things and they sell it and invested in Bitcoin,  a few days ago a person on this forum has also invested in bitcoins by selling some cows from his father farms. There is nothing bad in this if you have something that is extra or does not make any burden if you sell it same is with you,  you have nothing apart from and you sell it.  Hope you will gain the goal from which you sell your computer.