Computer Keeps Crashing - Working audio and striped screen.

My computer keeps crashing. Sometimes I get a random striped screen. other times it will go solid white. sometimes it goes blue but its not a bsod, its a lighter blue. sometimes It will reboot itself. It usually happens when playing games but sometimes happens when browsing or when playing songs on wmp. Ive uninstalled drivers and downloaded new ones, reset my system to factory defaults multiple times. hasn't gone away. I have a minidump file I believe if that will be of any help. here are my system specs:

Alienware x51

-Intel Core i5-4440 CPU @ 3.10 ghz
-AMD Radeon R9 270 2gb gddr3 (unsure about dedicated ram)
-8gb Ram (unsure what brand)
-Windows 8 64 bit

any help is appreciated greatly, as I just bought this pc and id like to be able to use it. thankyou in advance