upgrade and new build - help?

I just upgraded my PSU and I have another computer I'm building but need a motherboard, PSU (for it) and video card. I haven't chosen those components yet but the rest are already purchased.

I have some problems with the PSU upgrade because I didn't put the current computer together. I let a store vendor do it. I've been having really bad luck with store vendors lately. I also discovered that my RAM are different speed configurations even though it's the same brand (OCZ). I feel scammed. It's been so long though since I had the computer put together that it won't help to complain now.

Anyway, can anyone advise how I can figure out how to connect which cables with what hardware?

I can figure out the easy stuff (main power, GPU power, fan power cables) but there's a bunch of smaller cables that I don't know what to do with.

So far, my computer won't boot up properly now and it just stops at a Nvidia ethernet controller boot screen (DHCP) and I have no idea what the problem is or what other problems are present. I am sure there is some cable that is not yet connected and I am not used to SATA connections. My DVD burner is probably not properly connected and my 'lights' for the power aren't yet connected.

I'm going to take a look for the motherboard manual and if I can find one, a manual for the computer case. I am hoping this will help me figure some of this out. If anyone has any suggestions, advice or explanations, please offer!!!!!!!

I appreciate any comments, advice and assistance. Thanks in advance.

P.S. I would like to figure out how to have my current computer running well and connected properly. I'll deal with the new system later but I guess I should post in the appropriate categories/sections for that?

The current computer that is already built (other than the upgraded PSU and graphics card) was working fine before I got a new GPU and PSU. But, now, I am having some issues since the new PSU was put in there.

I assume it's from incorrect connections.

I connected the HDDs (2 500GB SATA drives) with a modular PSU. I connected the hard drives with the connectors given in the PSU box and connected from the hard drive directly into the PSU power connector 4 pins in the modular inputs. I hope that's okay.

The other concern I have is I forgot how the rest of the connections go since I unplugged the old PSU. I have a couple of tiny but thin two slot (?) cables that plug into two pins somewhere on the motherboard. I assume these are for fans or PWR/LEDs.

I am now looking at my motherboard manual trying to figure out where they go. One of the smaller cables is from the case/chassis. The other orange cable I've been trying to trace. It is near the other 'spiral' type of cables.