Problem starting up my thinkpad lenovo?

When I try to start it up it goes to it's normal First thing [which is just the page with just it's name and the interrupt the start-up] and then it goes to a black screen with a white underscore which just keeps blinking, we tried leaving it on all night, that didn't work, then we tried repeatedly pressing enter, then the space button, what should we do?

Added (1). And I should add I tried to do a system restart before this problem, when my computer said I had a Trojan virus.

IBM sold their problematic pc division to the Chinese.

System restore your computer, that may fix it.