I assume the cables you refer to from the case, are the power switch, reset button, hard drive indicator, etc.  They should all connect to a small block of pins on the motherboard, but I think I had one with mine I didn't use.  There may also be a cable from the case to the motherboard to connect the front USB ports, if the case has them.

As far as your problem goes, I'm no expert, but the first things I might check is that the CPU, Heatsink and Fan are fitted correctly, and that a) the memory sticks are seated correctly, and b) that you have the correct memory for the motherboard.  It might be worth taking out one memory stick, and see if that makes any difference (you can always add it again later), or change the position of the memory sticks in the slots (i.e., try slots '2' and '3' rather than '0' and '1' depending how many slots you have).  Some motherboards prefer the memory a particular way round, but I believe the usual configurement is to fill from slot '0' first.

Hope that might help, but I expect a proper techie will be able to help you much better.

Oh, and    

A common problem actually, with all types of solutions.


First of all, make sure that the BIOS (CMOS) has been cleared.

Make sure all jumper settings are correct for your CPU speed etc.

Make sure that your PSU is big enough for your rig (300W minimum these days).

Take out items one by one until it works.

I've found these faulty items can cause the issue:

CD-ROM
HDD
FLOPPY
MEMORY
CPU
MAINBOARD
MEMORY
GFX CARD

and the biggest problems:

PCI modems.


^ yes thats nearly everything!

Strip your system down to:
mainboard
cpu, heatsink, fan
1 memory stick
gfx card.

and see if that works.

Then start removing the gfx and memory. Test the power after removing each one. The fan should still spin without these (if one of these are faulty), but you will get excessive beeps.


GOOD LUCK!  

I understood what he had written, I merely wanted him to confirm, that what he had written is actually what was happening ..............I mean look what happened to the Light Brigade  

The 6 pins cable is probably for your Front USB   and the location is marked below  

sorry Tony, was only trying to clarify myself