I bought an old used computer and I found 130 bitcoins. What do I do?

First of all, you can’t really find bitcoins on a computer, as all bitcoins live on the public blockchain. However, you might have found a wallet app, or a private key giving access to a bitcoin address containing 130 bitcoins.

Semantics I suppose. But let’s say you really found access to 130 bitcoins on a used computer. Most likely, the previous owner of this computer was a tech savvy, early stage bitcoin investor, and will still have a copy of this private key on his new system. If he (assuming a he, since there were very few early stage female bitcoin investors) finds that some or all of his bitcoins have been transferred (by you) to another address, he will spend the rest of his life trying to track you (and his 2 million+ dollars) down. If he reported the theft and you try to cash out at a bitcoin exchange, you will likely get caught and arrested.

If you want to do the honorable thing and notify the original owner that his private key has been compromised, then transfer a small (but noticeable) amount to a new address, then wait several weeks or months. The owner would likely notice that some of his bitcoin has gone missing, and then bring the remainder of his bitcoin to safety by transferring it to a different address.

(that said, if the original owner was careless enough to leave his bitcoin wallet on his old computer, there will probably be identifying information on the hard disk as well, and it should not be hard to find out the original owner and notify him).

If you want to keep the bitcoin and not get caught, then transfer all the bitcoin to a new address, and use an anonymous or decentralized exchange such as Shapeshift to exchange the bitcoin for Monero, in multiple smaller transactions. Later on, you can then exchange your Monero back to bitcoin. Nobody will be able to trace the transaction trail any longer due to the fact that it is not possible to trace cryptocurrency on the Monero blockchain (unlike Bitcoin). Still, if you cash out large amounts of crypto to ultimately deposit into your bank account, you will likely attract the attention of the authorities. You may end up being investigated for money laundering or theft if you can’t prove that you purchased or mined the bitcoin yourself. Your best bet will be to spend it by making small purchases online directly with bitcoin, and/or exchange small amounts of bitcoin for cash using services like Fastest and easiest way to buy and sell bitcoins or purse.io.

If you go the latter route, be prepared for a life filled with paranoia. Even if you cover all your tracks online and on the blockchain, the owner might find you through tracing the ownership transfer of the physical computer that you now own. People have been known to go through great lengths to recover their lost bitcoins, so be warned.