Bitcoin wallet corrupted

I traded for most of my bitcoins, but I have also mined some. At first, it was possible to mine with the CPU on a PC, but so many people are mining nowadays that it's impractical unless you use a high-end GPU (on a graphics card). But Bitcoin is fundamentally a currency, not a goldmine.

For those who don't know the term "mining", it works like this. There will eventually be no more than 21 million bitcoins (although they are subdividable, so the actual number is of no consequence). These coins are represented by cryptographic codes that are "discovered" through a computationally difficult process that also secures the transactions being processed through the Bitcoin network. So far, about a quarter of the 21 million coins have been "mined", but difficulty gets harder over time so it will be about a hundred years before all of the coins are in the system. Because the uptake of Bitcoin will probably grow faster than the rate at which these coins are coming into the system, it's likely that there will be net price deflation.

It's absolutely not necessary to participate in mining to use Bitcoin. If you don't mine, Bitcoin works much like PayPal but better. Most transactions are free to process, and are irreversible once they have received enough confirmations from the network.