Blank purple screen after fresh install of Ubuntu 16.04 alongside Ubuntu 14.04

[nid-n10]

Hi


I am new to Ubuntu. I installed Ubuntu 16.04 alongside Ubuntu 14.04 on a computer that natively ran Window (essentially triple boot). After installing, I am able to login into 16.04 with my username but after that I am stuck with a blank purple screen. I have spent many hours already and read through many forums without any help. I even reinstalled Ubuntu many times. I have already tried CTRL+ALT+F4 to use terminal for functions like sudo apt-get update and sudo apt-get upgrade.


Here is some details I think might be helpful.


DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION_"Ubuntu 16.04.5 LTS"


Linux (username...) 4.15.0-29-generic #31~16.04.1-Ubuntu SMP (day and time..) x86_64 x84_64 x84_64 GNU/Linux


01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] RV370 [Radeon x600/x600 SE] [1002:5b62]
Subsystem: Advanced Micro Devices, Inc. [AMD/ATI] RV370 [Radeon x600/x600 SE] [1002:0b02]
Kernel driver in use: radeon


I tried running "env | grep DESK" but it didn't work. Any help in getting 16.04 working properly would be greatly appreciated.


Thanks