Trouble-shooting Why New Build Will Not Power On

Hi. Hope I am in the correct area for this. Just to express my technical skills, I have built a few pc's several years ago. So, I am not unfamiliar with the basics. Times have changed and things have gotten more technical and SATA has taken over IDE

My delemna:

Gigabyte GA-MA790GP-UD4H motherboard AM2+ Socket

2 Sticks Crucial 2GB 240-pin DDR2 SDRAM DDR2 800 Memory

AMD PHENOM 9950 Agena 2.6Ghz

Thermaltake v9 Gaming case

Thermatake W0116RU 750 W PSI

After careful placing of CPU and heatsink/fan and RAM and connecting 8-pin power connector and the 120 pin to motherboard, I get nothing when testing the power. The cpu fan will give a little twitch----and that's it. I realize I won't get far without hard drive connected, but I am under the impression that I should at least se some lights and the fan go into action. I've seated and reseated the CPU and Memory sticks but to no avail. I don't know why I thought that the motherboard had on-board graphics and neglected to get a graphics card ( PCI Express slots). So there is NO graphics card in place yet.

Still, I thought I would get some action to verify power. Nothing!! Now I am worried that the mobo, processor or PSU is dead. I googled like crazy and haven't found a hint as to what I may have done wrong. The 2 power connections and cpu should at least show life in the system, right? Maybe some silly little thing I have forgotten? I hope so!! Anybody able to give me some direction? I would appreciate it big time. Thanks

Al

Thank you. It IS a good start. I have just read the link and the breadboarding procedure. Will now start doing a thourough check, bit by bit. I would hate to bring it in to a PC shop only to find out it was a simple fix.

Thanks again.
Al