Need Help - Computer Case

You already have everything sorted, plug it all in!

The LED's work only one way, if they don't work reverse them.

Your case's power LED is two pin, it needs to be 3-pin to fit that connector.

The missing pin on USB is a shield pin, so now you even know which way those go.

I seem to have got it to power up and into windows. Only problem i'm having now is getting the computer to shut down, and the power supply fan doesn't seem to be working.

I used the following wires in this order to start to the computer up

Front panel connector

Ground, L-RET, R-RET, "space", Mic Power, Mic In, L-OUT, R-OUT

I've noticed that the system fan connector hasn't any wires in it and i've got a reset sw wire and a power sw wire which i haven't got in anywhere yet.

LOL, OK, I thought you had it sorted out. Look at your diagram. The first three pins are for the Power LED, then a space, then the hard drive LED, then DC SW means the same thing as Power SW.

I only have a power sw and reset sw though

the only thing you really need connected is the power switch (power SW), which connects to the DC SW pins.

In order for me to get the computer to start i need to have l-ret, r-et in 2-3

1 2 3 - 5 6 7 8

I also need to have l-out + r-out in 7 + 8. I've tried putting the power sw in 7 + 8 and l-out + r-out in 5 + 6 but it didn't work.

NO, you're doing it all wrong. L-Ret and R-Ret are AUDIO CABLE WIRES! You NEVER need those connected to ANYTHING to make the computer operational.

Your front panel wires are JUST LIKE YOU SHOWED THEM:
Power LED (1-3) are for the light on the front to show the system is powered up, this isn't needed to make the system boot, but is handy for showing it's on.

HDD LED is for the hard drive light on the front panel. It's also not needed to make the system work, but should flash when your hard drive is being accessed.

DC SW is for the power button, and IS needed to turn the system on.

DISCONNECT EVERYTHING as you have it all wrong, then put the Power Switch wires (PWR SW) on the DC SW.

The order is: PWR LED on pins 1 and 3, HDD LED on pins 5 and 6, PWR SW on pins 7 and 8.