why does the bitcoin client generate new addresses every day even though i didnt tell him to?
Are you performing transactions? How are you determining that the client did this?
if i want to move my wallet to a another computer do i just install the bitcoin client there and replace the wallet.dat file?
or is there a way to merge two wallets into one?
If you're replacing one installation with another, just copy over the wallet.dat file. Otherwise, the easiest way to merge is just to transfer the bitcoins to an account that's already set up on the other computer.
