Acer Aspire 7520, sudden boot problem

[Refia]

I just bought an Acer Aspire 7520 (exhibition piece, used - like new) and received it in the post yesterday morning. After a whole day of running fine, I used a friend's T-Mobile Web'n'Walk usb dongle later in the day and about halfway through install the system froze (except for cursor motion, I couldn't click on anything). I forced a restart, and after the initial boot screen it was left on an almost completely black screen with a white blinking underscore in the top left corner, even left for a while this didn't change.

I've tried restoring default settings in the f2 Boot Menu, leaving the system shut down over night, but nothing else so far as I don't want to damage it further.

Please help!

 

[Tmagic650]

The hard drive data may be corrupted, or the hard drive may just be bad. Pull out the hard drive and see if you get a display of the initial post