I have the old Bitcoin client 0.3.20.2 BETA
It was all backed up and I ran the program on my new computer but the bitcoin address is different. There doesn't appear to be a way to manually change it back to the old one.
Which program did you run on your new computer? I assume you have an old wallet.dat, which would load in a modern
Bitcoin Core. This will take a long time to download 150 GB, but it will quite quickly show your transactions from 2011.
If your wallet.dat still works, this is the way to go. There are other possibilities (extract private keys for example), but without more information about what files and software you're using that's just guessing.
There is a file that is called mykey.txt and I tried to transfer it to a new wallet and it shows my bitcoins but it is "watch only" and requires the private key. I thought that WAS the private key.
How do I get the private key from this old client on my new computer?
If your mykey.txt doesn't hold private keys, your only chance is your wallet. Start searching there.
In 2011 Bitcoin was worth $1 to $10, if you find a few in your wallet you're looking at $7700 each. What made you forget you had that wallet all these years?
I have the client / wallet called "Bitcoin" version 0.3.20.2 BETA. It is a wallet and mines as well using CPU.
I didn't forget I had the wallet, I've been keeping my eye on it and had it backed up in 3 locations, but I never tested it on a different computer. I would open the wallet occasionally and see everything still there. Apparently backing up "mykey.txt" and the application and all its data wasn't enough and "mykey.txt" is a public address I'm finding out now. I can see my coins but the wallet.dat file you mention is not here. I just did a search and it's located in /roaming/bitcoin/wallet.dat
Arg, thinking of it now because of the price. My backups are useless and I just formatted my computer 2 weeks ago. Looks like I'll be doing some unerasing to try to find that wallet.dat file. Thanks, but my easily mined free coins are most likely lost forever at this point.
