I apologize for the delay getting back to you. I have been offline the last few days.
Since reading your reply, I have been unable to find a manual for your machine.
As a result, I cannot provide as specific directions as I would prefer.
So... General Instructions...
Unplug your machine.
If necessary to move it to a place where you can work on it, unplug your keyboard etc, taking note of which plug attaches where.
Once you have removed the case cover, and before you have touched anything inside the case, make sure you have grounded yourself (to discharge any static), by touching /holding the bare metal of your case or power supply.
Hopefully, there will be enough free space between components that you can see your motherboard clearly.
You will see cables that connect to power supply, and others that connect to drives.
Some may need to be moved slightly to see better. Be careful not to disconnect them in the process.
Once you have a view of your motherboard, take a moment to get oriented.
You will see a large heatsink and fan. These are to keep your cpu cool.
You will see some slots for memory chips.
You will likely see at least one other major heat sink (for on board graphics, and/or io functions).
Somewhere on the board you will see a small flat battery, about the size of a US nickel.
This battery allows the BIOS Chip to retain its settings if they have been changed from factory defaults.
This battery is usually close to your BIOS CMOS chip.
The BIOS Chip will likely say something like Phoenix, or AMI.
Sometimes near this location you will also find pins, which when shorted, will reset your BIOS CMOS to factory defaults.
Lacking specific information on your motherboard, and unless these pins are clearly marked,
you MAY be able to accomplish the same thing, by sliding the CMOS battery out of its holder
and leaving it out for several seconds, before reinstalling it.
This USUALLY will reset your bios to factory defaults, and your mistake will be undone.
Before closing up, do a test to see if you get your video display back.
If not, let me know, and also see if you can find information about your motherboard, and we will try something else.
See if you can find any information about the maker of the board, the model number and the serial number.
These will usually NOT be the same as the number you have already given me.
If it is a proprietary Packard Bell motherboard, we may be no closer to fixing the problem.
Because what we need is a manual for it, and PB does not have a friendly site.
Again, my apologies for the delay. I hope this helps. Please let me know.