First of all: Fried mobo won't have actual burn-marks. Finger-touch is sometimes enough to render your mobo dead.

Those burn-marks you see can be nothing more than dust and oxidation. If there were power discharges that can make visible burn-marks, believe me, you wouldn't be posting a Q here. You would KNOW it's dead.

From what I can see, you don't get any POST or beeps.

Could be couple of things:

- VGA (you didn't say if you tested it on another machine)
- Memory (can make system not post - try removing it)
- PSU (try another machine's PSU on yours)
- and (off course) dead mobo

For the HDD... Check the jumpers on it. Most HDD's have jumpers to set it on different modes (no. of cylinders, CHS, normal, LBA...). LBA is the standard. All other mods are out-dated. Also mind the master - slave configuration.
There are BIOS settings that can be modified to suite the HD's capabilities. If they were set manually incorrect, the HD won't work. Best choice is to set all on "auto". If that fails, try disabling the all the enhanced stuff regarding data transfer (set it on PIO 0 mode). It's sort of "safe mode". If all that fails, it's not evil.... it's dead.

Q's:
Is the HD being reported in BIOS at all?
Did you test the memory on another machine?


Note:
If you have 2 HD's in one machine, and both are bootable, it can make a conflict. To have a bootable HD it must have an active partition. Some machines don't like having 2 active partitions.

Some HDD's tend to be unreadable on one machines after being partitioned on another. Actually, it is not the HD thing. It's an IDE controller thing.