NEM(XEM) How-to: No private key back-up? No problem.

(Image source: Hive account@the-ultimatum)
BEFORE ANYTHING YOU MUST HAVE AT LEAST 1 COPY OF THE EXPORTED YourWalletName.zip FILE!

https://twitter.com/WavesIs/
XEM Post 1: Where does one look for support when one uninstalls one's wallet, Hive account@java & Hive account@firefox? You don't go to SlackHQ channel.
XEM Post 2: No private key but a *.zip backup? Edit the install location importing *.wlt & *.abd to accomplish a successful wallet recovery

• Recently my NEM Launcher was not working. NIS could not connect and was given an error code dealing with java runtime
• I uninstalled Java 8 and reinstalled it just to run into the problem that the NEM Client Launch file couldn't find the new Java install.

After a couple half days of frustration I finally figured out WHAT needs to be done.
Below are the steps I followed after reading an incorrect NEM Forum Post and my intuition.

1. Uninstall NEM(XEM) completely
2. Uninstall Java completely
3. Uninstall Firefox, especially if you have implemented security add-ons/plug-ins
4. Restart your computer.
5. Download & install Java 8 (jre-8u101-windows-x64, or the correct one for your OS).
6. Download & install the newest NEM(XEM) wallet. (https://bob.nem.ninja/installer/nemwallet-0.6.79-windows-installer.exe)
7. Download & install Mozilla Firefox
8. Restart your computer.
9. BEFORE adding security add-ons/plug-ins (*NoScript, Disconnect.me, HTTPS Everywhere, Privacy Badger) open the NEM Wallet Launch file and make sure everything is installed correctly.
10. If everything is installed correctly NCC/NIS should open in the browser and start downloading the blockchain from the beginning.
11. You can exit out of this.
12. Now unzip YourWalletName.zip file and you will see 2 files: YourWalletName.wlt & YourWalletName.adb
13. Open the NEM Client install file location.
14. Delete the file ncc.lock file.
15. ADD the two files: YourWalletName.wlt & YourWalletName.adb to the main folder.
16. Redundant: Since I could find no up-to-date article and the v0.6.77 files are different than the updated v0.6.79 files I copied and pasted the two files (YourWalletName.wlt & YourWalletName.adb) to the folders:
    mon
    ncc
    nis
17. Restart your computer.
18. Open your NEM Client and if all is done correctly you will click on "Open Your Wallet" and your old wallet should be preloaded.
    That is what worked and worked perfectly for me and hopefully you too.

Is there an easier way?
Yes. SAVE your private keys for your wallet that you just installed.
ENCRYPT it on a separate device or print it out, throw it in an envelope, slap a To/From address and correct postage to add an extra level of security if needed.

United States
Local LE doesn't have jurisdiction over federal USPS mail.
Also if you catch someone breaking in and rifling through your possessions if the criminal opens your mail it's an automatic felony.

I hope this adds some clarity to a convoluted issue.