Exactly!             


There are two wallets:

wallet #1 (savings wallet  on USB drive that I created following the steps here: http://startbitcoin.com/how-to-create-a-secure-bitcoin-wallet/    .

wallet #2 that came with bitcoin client.


A couple of months ago, I sent some bitcoins to my #1 wallet address, and and now I wanted to update it. I just booted Ubuntu from USB drive and installed Bitcoin Linux version.
When I opened Bitcoin, I first tried to delete wallet #2 that came in .bitcoin folder in order to paste my #1 wallet from USB stick.

For some reason, I was not able to delete wallet #2, or paste my savings wallet.

Also, when I tried to open wallet #2, I got the message:

Could not display “/home/ubuntu/.bitcoin/wallet.dat”
The file is of an unknown type.

When I first went through this process a few months ago, everything went well. This time, I am making a mistake somewhere.