Hi,
I've just built new PC consisting of

Asus M5A 78L-M MOBO
16GB DDR3 1333Mhz        (INSTALLED by vendor)
AMD FX8150 3.6GHz CPU (               "               )
PSU:  XFX Pro 650 w
Antec 300 case
Samsung DVD RW sata drive
3 used sata hard drives   

Booted up no problem. Tried to install Win 8 which said (I don't remember the exact words) none of the drives were suitable and wouldn't TRY to format them They were all working prior to this.

Sooo..... I thought I'd try to format using an xp disk. It was quite happy to have a go but while I was off making a coffee everything went dead. I tried to restart but nothing happened. The green light on the mobo  was on but nowt else.
Asus site suggested reset cmos   - no good
                               disconnect everything except mouse - no good.
When I reconnect the mains lead and try to switch on the mobo green light comes back on and the psu fan and the cpu fan + case fan all move briefly but they're the only signs of life.

Is this a 'send the mobo' back situation?

Thanks,
Geoff
All MBoard standoffs in place ? ?
4 pin power CONNECTED to CPU ?
Thermal paste applied properly ? ?

If yes to all the above try and bench test it out of the case before giving up on the MBoard...
BTW...is that a new or used PSU ?Yes, stand-offs in place, 12v supply connected, psu is new; cpu, cooler & memory were bought as a package, already assembled .   CPU assembled by whom ? ?
Have you tried it with only 1 stik of RAM ? ? The single stik should be in the slot closest to the CPU........and the reason I bought the mobo etc as a package was because I've had trouble in the past putting coolers on amd CPUs  because they do up so tight I think something's gonna break (even when everything's seated right!!) .
.....just seen your reply, Patio.   Assembled by a company on ebay:
 http://myworld.ebay.co.uk/envizage2000?_trksid=p2047675.l2559Just tried your ram suggestion but no go.Not familiar with the seller at all...but it could be either the MBoard and/or the CPU at this point if all i suggested was tried...
I'd start up the return/warranty process immediately...Yep, I might try out of the case first [when I clear some room]. Thanks for your help.Anytime...Welcome Aboard...and bring us good news...

P.S.S....On the benchtest also try another PSU...i've seen them DOA as well...Hee hee!
Patio,  good suggestion about the psu...... connected up an old one and pc booted no problem.
Thanks again.Excellent ! !

Well not really...now you have to RMA the PSU...
           
But seriously...good news.