Computer Shuts down at Log in Screen!!

[keapachi]

I installed a new graphics card and after a couple of days i turned on my computer and it loaded to the log screen and froze and just went blank saying no display then i switch the computer off in the back and wait 1 min and turn it back on and it works just fine until the next time i turn it off. Could it be my Power supply or the graphics card it self?

 

[norcalsc]

We don't know what you are working with. Specs please be detailed