Black screen flashing line top left

[computerwonder]

Ive just rebuilt my computer into a new case and has worked flawlessly for 2 days now no problems, when I came to power on this afternoon I got a black screen with a flashing cursor. I noticed I had my external hard drive plugged in so I removed it and powered up the computer again. Its all working fine now but any idea to what happened? and did my external hard drive cause this?

Should I be worried?

 

[alexoiu]

No, you don't have to worry. The system tried booting from the external HDD and didn't find an operating system (like Windows).