Dell M6300 not booting

[loudmacleod]

I have a Dell M6300 that I inherited from my company. The screen has been turning off and on for a split second for several months. It finally stayed that way a week ago. Knowing it was likely the inverter, I purchased a refurbished screen assembly to keep it simple for repair. Today I replaced it but now can not get the machine to boot. It powers up, I can see the backlight of the monitor now but that’s it. Any suggestions?

 

[loudmacleod]

One other thing I verified today - I had a SATA to USB cable to make sure that the HDD was still accessible. So the question now becomes, what could possibly be preventing it from booting? Any hints? It is Windows 7.