car wont start after installing head unit!?

[vs calais 95]

Ok so I've just finished installing my head unit, i have a vs Calais, and the normal vr-vs ISO plug didn't work, so i was recommended using the vt plug, which worked perfectly so I've got it all back together and it was going all good until i try and start my car... the car doesn't start now, it just makes a funny clicking noise.. I'm not the best with cars seeing as this is my first one and no prior experience. All the accessories are on and all the other lights.

I'm thinking either,

1) Battery dieing?

2) vt ISO plug causing problem?

Help would be appreciated as i want to get my car back in action asap! lol cheers.

[vs calais 95]

all good, was just flat battery haha

[Coast_Calais]

LOL, i was just typing about to say, "erm, you got a flat battery mate"..

[kiwiss5L]

yeah would be a bit worried if ya head deck was shutting off your car haha. i run my battery flat when i was installing mine one night.