Here's a guide to flash the 920, but it should be about the same for the 830:
http://forums.windowscentral.com/no...after-reset-flash-process-defined-inside.html
I found NokiaCare on my Computer, here's the download:
https://drive.google.com/file/d/0B3Y...ew?usp=sharing
Here are the steps edited for the 830:
1. When complete, browse to: C:\ProgramData\Nokia\Packages
2. Create a folder called Products
3. Create a folder called rm-983
5. You should now have a directory like: C:\ProgramData\Nokia\Packages\Products\rm-983\
6. Browse to the Download folder you extracted
7. Copy the entire folder contents and paste it into the C:\ProgramData\Nokia\Packages\Products\rm-983\ directory.
NokiaCareSuiteForStore-5.4.119.1432 Directions:
1. Launch Nokia Care Suite
2. Click the Product Support Tool for Store 5.0
3. Click File
4. Click Open Product
5. Choose RM-983 (Nokia Lumia 830)
6. On the bottom left click Programming
7. Click Recovery
8. You should see the firmware you downloaded and copied earlier under the Properties field.
9. Click Start
10. The software will check the package contents, it will fail to find the phone, and ask you to reboot and give you a button to click retry.
Phone Directions:
1. Plug the phone into your PC
2. Hold the Volume Down and the Power button, click RETRY on the Product Support Tools Window
3. After you feel a vibration in the phone immediately release the Volume Down and the Power button and hold the Volume up button.
4. Continue to hold the volume up button, you will see the software say "Rebooting"
5. After about 15 seconds you will see a top NOKIA logo and the software will start flashing the phone.
Now, I have NOT TESTED THIS. If someone who knows what he/she is doing can test it first, then I'd really appreciate it.