Help needed with diagnosing a boot problem

[Obviously]

Having a problem for the past week with booting up my system. Fans and lights all come on but thats about it. I noticed that the HDD didnt seem to be spinning up.

I swapped out the sata cable and it started up fine but after shutting down I had the same problem. I went through 5 sata cables somtimes with start up and sometimes not.

I even tried a different HDD but still had the same problem.

Both mobo and gfx card are less than a year old so I dont think its either of those. I'm at a loss at this point really, any ideas?

Cheers.

 

[Obviously]

no, monitor doesnt even get a signal

 

[Obviously]

System Specs:

ASUS P5KPL SE mobo
Q6600
2x1GB RAM DDR2
4890
WD 500 Gig

No LEDs to indicate problems. No change when I swap the RAM around.

I didn't make any changes or install any new hardware before I got the problem. Something else I noticed is that my system definitely sounds different when it doesn't boot, but all fans are spinning ok...