Forget the old backed-up file on my PC with Litecoin in it.

[JMASTERJ]

I have an old backed-up file on my PC with Litecoin in it... I can't remember what wallet/app I used to mine and save it... It's a .dat file

How can I access this again and send it to an exchange or Ledger etc...?

[mocacinno]

A .dat file... My best would be the reference client... the one you could find at litecoin.org

https://github.com/litecoin-project/litecoin

As long as you make a couple of copy's of the .dat file on OFFLINE media, it doesn't hurt to try every available wallet untill you find one that works... That being said, for an older .dat file, litecoin core would be a good first step...

[JMASTERJ]

Is there is any way someone can steal my LTC while I am trying these wallets?

[mocacinno]

Well... that's actually a pretty good question...
In theory, yes, you can lose your coins while trying out wallets.... IF you download a fake wallet, and import your wallet file, i guess you can get robbed... Also, if your wallet.dat is currently residing on an offline machine, but you move them to an infected (or improperly secured) online machine to try to import them into a wallet, you can get robbed aswell.

However, there are ways to decrease your risk:

• you can run litecoin core on an offline machine using your wallet.dat, then export the list of addresses to an usb drive (or, if you're paranoid, generate a qr code of your addresses, and scan them using your mobile device) and then look those addresses up on a block explorer... If they are funded, you can use an offline setup. Here is some info on how to do this using bitcoin core (but litecoin core should be more or less the same) https://en.bitcoin.it/wiki/How_to_set_up_a_secure_offline_savings_wallet
• you can verify the signature and hashes of the wallet files, and only download them from official channels
• you can make sure your pc is clean, updated, firewalled,...