Problem with my GPU

Hi guys!
I'm having trouble with my new GPU (R9 280x). Long story short. Last month I bought the GPU, but couldn't use it because I had a shitty PSU. So today I bought a new PSU (Antec High Current Gamer 750w) and I connected the new GPU. First boot is ok, used to have catalyst, so no big deal about drivers. But when I opened a game it crashed before it even started.
Then I restarted the PC, but I couldn't boot past windows 8 logo. When Windows 8 user password screen should come, my screens starts blinking.
I tried using the onboard gpu, and everything is fine. Tried uninstalling AMD drivers, but got same results. Don't know what else to try!

please list

  1. make & model of motherboard
  2. CPU  make & model
  3. amount of installed ram & speed  ....  like 2X4GB DDR3 1600
  4. GPU make & model
  5. old PSU make & model & wattage

and let us know if you tried GPU with old PSU

Solved! Was driver problem.. had to uninstall in safe mode, thx anyways for your help!

Dam I'm good  ... post if I can do anything else for you ...   lol

uhh .... I mean WTG