I found a fix that works for me and I have yet to have a crash since implementation.
My issue was that my ASUS R9 290X would crash while watching Youtube, browsing web, and some older games.
However when playing newer games it never crashed. I worked on this for 4 months, digging through post after post when I found a little secret in a comment of a youtube video. After nearly a week to make sure I wasn't being fooled, I am now confident enough to share this fix with you. Hopefully I will save someone from great woe and gnashing of teeth.
First I'll explain the problem, and why this is happening. (to the best of my knowledge)
R9 290 and R9 290x series cards run extremely hot, to the point where manufacturers were under clocking the 2d GPU Clock and Memory Clock to bring down idle temperatures. What happens is because the clock is so low, the voltage drops due to not being needed, said voltage drop triggers an under voltage situation, causing your pc to crash or shut down and restart due to under-volt protection. basically you're not running the gpu enough, I think this is also causing the video driver crash error some people are getting too. VLC media player used to crash my pc anywhere between 1 minute and 20 minutes after starting a video. Now it doesn't after hours and hours. Same with Youtube, or games that still use a good amount of 2D Hardware. Minecraft (think of the menus, all 2d) Titan Quest (the hud and menus are all 2d) These would crash often, but not other games. BF4 ran and still runs like a dream. Far Cry 4. Runs on ultra 1080p with only slight dips below 50 fps during driving. I think newer games use very little to no 2d sprites, so they don't cause this crash.
The Fix:
I don't think new drivers are necessary, but I have the latest OMEGA Radeon drivers, and the latest bios for my GPU.
Mine works, so I can't confirm these are required steps, but I recommend them. Maybe do this first, if you want.
Then download the latest version of ASUS GPU Tweak. Can be found on ASUS Support website. If you have a MSI or other brand card, download MSI Afterburner or equivalent. I can confirm ASUS GPU Tweak works, because it has the 2d option. I can't confirm MSI Afterburner has this, but I'm sure it does. refer to MSI Afterburner help to see if it has 2d settings.
Before Installing GPU Tweak or equivalent, go into CCC (Catalyst Control Center) and disable AMD Overdrive so It doesn't conflict with ASUS GPU Tweak or MSI Afterburner. Don't worry. If your card is stock overclocked, it will retain it's stock overclock. I am not confirming they conflict, this will just prevent it, since you now will be using Afterburner or Tweak to control clock and fan settings from now on. CCC will still be used to adjust graphic options for games etc. Some folks don't even use CCC...
After disabling AMD Overdrive, install GPU Tweak (or afterburner)
Use internal updater to make sure you have the latest version. go into options and set it up to start when windows starts, and I chose to have it minimize once opened, so it's not in the way on startup.
You'll see a overly fancy red window with a giant tachometer on the top. Under that you'll see a Red button that reads "3D", and to the right a description of the card you have.
Hover pointer over the 3D, click 2D. Now you can change the 2d settings for your card.
Change GPU Clock to 430 MHZ. I recommend typing in 0430.
Change Memory Clock to 900 MHZ. Again, type as 0900....
(not required) I also recommend Defining an new heat to fan speed curve, as I think the stock one sucks. Click the little gear by user define.
Important last step:
Make sure to save your new 2d settings, and if you chose to your new fan curve to a profile, you'll have to select that profile every time you use your pc.
Caveats:
1. You could RMA your card, but it takes forever and you might get another back with the same issue. I did this and I'm content. (I've been trying to figure this problem out for 4 freaking months, needless to say I'm pleased as punch.) I even thought it was sub-standard power in my house, or my CPU, or my RAM... lols. A new build nightmare.
2. This mod will fix your problem, but bring your idle gpu temp up. Make sure you have adequate cooling. Is your case cramped? Jungle of wires?? Clean it. Maybe change your thermal compound on your cpu, and clean everything. Fix that jungle... My idle temp of my gpu went from 38c to 47c.... Not a big deal for me at all. Under load there will be no change in temp. If bf4 took it near 90c, that won't change.

If your cpu is on the verge of overheating, or other components, make sure you're ready for a jump of 10c or more on a cramp dirty case. my cpu is on water, so I'm not concerned about 10 degrees..
3. If you think it's a pain in the butt to click profile 1 on GPU tweak when you turn on your pc, RMA your card.
It's really not a big deal and takes minutes to install, and seconds every time you turn on.
4. Don't close ASUS GPU Tweak after clicking your saved profile. Clicking the X closes it completely and shuts off any changes you've made. GPU Tweak will need to always be running in the background, but uses little resources anyways. I'm not sure if MSI Afterburner works the same way, and you need to keep it open. Just minimize it. Someone with an MSI card, and issues, should try Afterburner and report their findings.
Again, this took me 4 months to figure out, I hope I can get you fixed in 30 minutes...
Thanks again for everyone's input.
Let me know if you have any questions or problems.
Cheers!
Matt
Oh and to update, here's the thread that I first created back in September showing all that I was completely on the wrong path in the beginning.. lol
http://www.tomshardware.com/answers/id-2303442/windows-random-crash-reboot-windows-error-codes-reasons.html#14908917