Mac Mini (Mid 2009) boots to grey screen (no Apple logo)

So my Mac Mini isn't starting up all the way. I power it on, hear the chime, then it just sits at a grey screen. Here's what happened:

I come home, Mac Mini is still booted into the OS X 10.11. I reboot it into the Windows 7 partition, check for updates and see if the Windows 10 install is ready. After finding out that it is not, I click on the bootcamp start up manager and choose to restart in OS X. Computer reboots and that's when it starts booting to the grey screen only. Sometimes the display I have it connected to doesn't see a signal either.

Here are the specs of the system:

Core2Duo 2.4GHz

8GB RAM

I have removed the optical drive and have installed a second HDD. An SSD to be exact.

HDD #1 is a 500GB that is split in half, one with 10.9.4 installed and BOOTCAMP (Windows 7)

The SSD (256GB) has OS X 10.11 (Public Preview Build)

The system was working just fine up until last night, no new software was installed, no new updates or anything.

Here are the troubleshooting steps I've gone through:

1. Attempt to boot to the start up manager, tried with both a wired and wireless (bluetooth) keyboard. Both keyboards are Apple branded. Got no response from either.

2. Tried booting into verbose mode to see if I can see where it is hanging, no response from keystroke.

3. Held shift to boot into safe mode, no response.

4. Reset PRAM/NVRAM, no response there either.

The only thing I haven't done yet is pull the HDDs out of the system to make sure they're okay. From the research I've done, it sounds like the EFI is busted, or something else.

I know the keyboards work as they work perfectly fine with my MacBook Pro.

If there is anything else I can try, please let me know.