No Power Nothing Nada Won't Even Boot?

Hey There-
Can somebody please help me...I think I'm loosing my mind?
I have built five systems total in my life, all AMD based, and all using MSI Motherboards...with the exception of 1 ASUS/AMD build. I recently purchased an AMD Athlon 64 Socket 754 3000 CPU, along with an MSI K8N NEO motherboard.
After setting everything up, my IDE 1, IDE 2, connections, both ATX 20-PIN (JWR1), and ATX 12V(JPW1) ATX power supply connections which link to the motherboard I "Thought", my newest creation would "Boot"...so much for wishful thinking.
Nothing Nada, so after hours of "Playing Around", I decided to take my MOBO/CPU to FRYES to get it tested. The result everything worked like a charm...wish I could say the same when I brought it back home and hooked everything back up. After I hooked everything up once again nothing happened. I thought maybe I would try a new case, and a new Power supply, so I put my MOBO/CPU into a new case, and still nothing nada.... what the heck is going on?
In every other system I have built as long as the ATX power supply is properly plugged into the Motherboard, and the heat sink/FAN of course is properly plugged into the motherboard, my system would at least turn on. I get nothing no power…nothing CPU won’t “SPIN”…Nothing I’m “Perplexed”? Could it be I need to make all necessary connection in relation to motherboard jumper setting etc…maybe some kind of short…But in both cases I highly doubt it.
Please someone help I will be eternally grateful…..and I promise to pay whomever gives me the solution to my problem $25.00 via Paypal, money order, cashiers check..ETC…I’m “Dead Serious”. Please feel free to email me at excelrye@earthlink.net
Warmest Wishes,
Ryan

Since you verified a working mo/cpu. That's not the issue, have you verified that the power supply works, as in test it with another system?

I remember the first time I worked with MSI mo, I(natuarally not reading the directions x_x), didn't see to put the addition power cable on the mo, but this at least made the cpu fan spin for 10 seconds before shutting off. Although that was a P4 board.

As simple as it sounds, check the memory. But for the main part, my recommendation is to break everything down to it's simplistics, the bare essentinals of what you need(ps, cpu, mo, mem, hd, graphics). And see at least if you can power there.

Try the switch to the other power supply voltage?

I feel really stupid....I hooked up all my connections POWER LED, HDD LED, POWER SWITCH to the motherboard....and "Wallah"....it worked! Now I need to get my CPU TEMPS down from 49c/120f to around 30C...Freaking thermal pads stink!