My guess is that the HD cooler fan was drawing too much power at startup (from a cold boot), but when you warm booted, residue charge somewhere let the computer start normally. (this is something like where I remembered reading abot residual charge before)
It's only a 300 W PSU, and you have two hard disks, so that
may have been the cause, but I don't know the ratings of everything, I just know that by comparison 300 W is weak, but maybe the fan is just faulty and drawing too much current.
PS now I wish I had a (decent) digital camera again
.
PPS it looks like the exhaust fan is starving the CPU fan (pm
me for more info).
PPPS that's a cool CPU heatsink.
PPPPS the northbridge heatsink at an angle looks cool as well.
PPPPPS mmm ... red mobo
PPPPPPS lots of PSs in this post