The most important thing is your 33 word wallet seed. As long as you have that, you can always recover your wallet on any computer from anywhere in the world. If you are using the command line utilities (dcrd/dcrwallet/dcrctl), your wallet file is located in C:\Users\YourUser\Local\AppData\Dcrwallet\mainnet But as I previously said, this file is not very important compared to your wallet seed. If you lost your seed, it's a good idea to have a backup of the wallet.db file, but you should create a new wallet where you can write down the seed and send your funds to it. If you have your seed, I wouldn't worry about backing up the wallet file itself.