What ist your real problem? How did you try to enable the VGA output?
Did you try an example design? Or your own design? As I can see in the 
data sheet the NanoBoard 3000 use a video DAC (THS8134B) to convert the 
digital color data into analoge values. So you just need to generate VGA 
conform signals...

Maybe this link give you some hints:
http://www.johnloomis.org/altera/DE2/vga.html

Duke

The error look's like using the name "VGA" twice (or more) for diffrent 
things. Can you rename one of you schematic?

Duke

Your promlem is written there:

1

Illegal value 262144 specified for DepthA

Somewhere in your System1 or Sheet1 or elsewhere is a memory or a fifo. 
But it is defined with to much elements (262144 = 2^18 = 18 bit wide). 
Try to reduce this.

Your approach show me, that is was right to abandon this altium stuff. 
It looks really nice, but hide the complexity of the underlying tools.
So first try to get things done without altium and later you can 
switch to use the fine assistances from altium...

Duke

I do all my (VHDL) development with the vendor tools (Xilinx in my 
case). It can even be used with altium hardware.

What is your goal? Why are you fixed on altium?

Duke

> the only tool that i have here is Altium Designer 9
That's not true. There is some underlying tool from the FPGA vendor. 
What flavor of Nanoboard 3000 did you have?

> This is my first contact with FPGA...
I see.

> I have in sheet1 18bit memory...
It seem's to big for your FPGA.

Duke

> I have in sheet1 18bit memory...
This is internal memory.

> this is the memory on the NB3000
> http://www.issi.com/pdf/61lv25616al.pdf
This is external memory. You need an SRAM memory controller for that.

Duke

> Is it possible for fpga to display .avi or any video files over VGA?
Sure. But try to make small steps:
* static VGA screen
* uncompressed picture on VGA screen
* compressed picture on VGA screen
...

I don't know the avi-algorithms, but for sure it's not easy to implement 
them in pure hardware.

Duke