Another change by modifying a letter in the file.
How did you change a letter in a .dat file?
After peeking at Op's post history here is what he did.
And I changed the file type,
For example :
a wallet.dat, which I had, was modified by software ... (it doesn't matter the software since the wallets are still there!)
Software has modified the file,
changing from .dat to .axx, and from .axx to .dat, after removing the software!
and going through .dat to .txt to read it too!
It's clear that he made some changes to the file while converting its been done via the software or by himself which corrupted the wallet.dat file and then qt created a new wallet which is why he is seeing different addresses. I am afraid there is an undo button for OP's fault and at least he should have created a backup before making changes so its a lesson and I assume the file is irrecoverable now.