If you have one of those USB VGA video card adapters, I'd try that to see if it will work, but this might not work if the system requires a password to boot, if its auto logon plug n play should detect this USB VGA adapter and give you a display to use externally to diagnose the problem internally. Other option is if Remote Desktop or another remote access program is available to connect to this system remotely to then diagnose further.
If the motherboard has a healthy boot to desktop, but display is shot, the USB VGA adapter that is plug n play should do the trick to have access to a desktop and diagnose further.
In the past when faced with problems like this, I try to find a twin on ebay that has a known good display but some other problem and then mix the good guts into 1 system and toss out the troubled guts and save the spare good duplicate guts in case ever needed in the future. However dont sink too much money into a project that can still lead to a non functional system. There is risk in buying a system to mix parts with that in the end you are still without a functional system and now out that much more money.
*Also, if the system requires a logon and you get the keystrokes correct, you can logon without a display to get the USB VGA adapter to mount up with plug n play and gain access to system if the main board is functional and OS is functional.
http://www.newegg.com/Product/Product.aspx?Item=N82E16815150177&SortField=0&SummaryType=0&PageSize=10&SelectedRating=-1&VideoOnlyMark=False&IsFeedbackTab=true#scrollFullInfo here is an example of one.
Edited by goldfist, 31 December 2013 - 10:00 PM.