Can I keep a computer, part of whose price (500 Riyals out of 2000) was paid with ill-gotten money, and donate 500 Riyals from lawful money to purify it, knowing that I use it for my engineering studies and fear that it might have a negative impact on my success and future earnings?

One must repent to Allah Almighty for acquiring money through unlawful means. Repentance is completed by getting rid of ill-gotten gains, either by returning them to their owner or their heirs, or by spending them on general Muslim welfare, or by giving them to the poor and needy if there is no specific owner.

There must also be intense remorse and a firm resolve not to repeat such an act. If it is impossible to deliver the amount to its owner or their heirs, it should be given as charity, and its reward will be for its rightful owners. Then, if they are found, they are given the choice to either reclaim it or accept it as charity. There is no need to inform them when they are found; rather, it is sufficient to deliver the amount to them by any means.

It is obligatory to give the money as charity if it was the price of alcohol or pork, or the dowry of a prostitute, or the fee of a soothsayer, and so forth. If these conditions for repentance are met, then the device becomes lawful.