Computer won't POST

[Hemodynamic]

I have a Dell 710 XPS that has been working fine for over 3 years and I have only had to replace a HD 3 months ago. Has been working fine since.
Yesterday was on the computer all day and was running fine with no issues. I do not turn off my computer unless I have to restart for updates so it was on all night but not in standby or hibernation (those options are turned off--Just the screen turns off and the HD's park their heads).
This AM I tried to "wake-up" the computer by moving the mouse but no go. Lights are on in the computer but no one home. So I reboot and the computer will not POST!! All the fans come on, MB light is on, all CD, USB, HD's and all fans are getting power. I can even charge all my peripherals (eg iTouch, GPS's).
I tore everything out of the computer, RAM, all cards including video, disconnected HD's, Opticals, fans, memory.
I took out the battery (battery fine) reset the CMOS, no go.
I inspected the MB and no blown caps (that I can see).
I reseated the CPU and checked the heatsink and fan all good (no weird smells either)
With the system bare-bones (only PS, CPU connected) no POST. I tried all possible configs except for buying new PSU, MB, CPU.
I need to know whether I should change out the PSU, CPU or MB because there appears to be no way to specifically test for which component is malfunctioning at this point and I don't want to drop a lot of money in case it doesn't work (why not just buy a new computer)
The cheapest is the CPU.
Intel Core2Duo 2.8 GHz $130
PSU 1KHz (I'm Running NVidia SLI, Raid 0 Drives, 4 Opticals, 4 peripheral cards) $180 or more
MB (NVIDIA nForce 590 SLI MCP-UY253)= $450 if you can get it.
Anybody have any ideas? Please help. I have spent the last 8 hours doing all that I can think of and all that I could read about and nothing.
Thanks in advance.

 

[Hemodynamic]

Thanks for the prompt reply. My question is how can everything be powering up fine (except the MB, CPU) and the computer not post?
One thing I have noticed from all the posts I have read for the last 9 hours is that no one can explain why things don't work just to, "try this" or "try that". I am just curious about things and like to know why things work or don't.
I would like to test the PS but a 1KW but again i'm spending another $50 for a 20amp multimeter (I know I'm a cheapy). All these years and no one has made an easy tester for all this. They make these computer diagnostics for cars why not computers.
Thanks again for your reply.

 

[Hemodynamic]

Any other suggestions or should I just take it to the computer guys and have them swap out the PS, CPU, and MB to see which it is.
Thanks in advance.

 

[Hemodynamic]

Thanks for your reply. I did all the testing and came out to be the processor or the MB (For all those who read this thread, if all your fans work on your computer eg. video boards, cpu, power supply, main case fan, etc. and all lights come on the MB and PS and front panel then it is 99.9% not your power supply). Anyway, took it to our local computer guy and found out it's the MB--$710 for the repair and no one has the motherboard in stock, refurbished or new. Computer is 3 years old and no one has the motherboard--proprietary MB it is (Yoda voice). Screw that!!!! That computer cost me $1000 per year and now I have to buy a new Comp. Done with Dell (bought it for the convenience). I will build my own again or buy from Tiger direct.
Thanks for the reply.

 

[g048989h]

Good thread!! build your own, you're more than ccapable and you'll get more value and performance, maybe even be able to use your good PSU, GPU's, HDD's etc. etc....
It's good to see some people still dig in and get dirty trying to figure it out before they ask for help.

 

[Hemodynamic]

I just want to tell everyone thank you for the support!!! The best option I found was. . . I called Dell support and extended my warranty for $275 for 13 months. This is Dell home support within 48 hours and would cover any and all repairs (they even said this would cover coffee, water or any liquid being spilled into my computer or even my screen being broken in half intentionally?) What!?! So no one has my MB in stock, my local computer store swore they could get it for $615 but they can't and will charge me $125 for installation. But now I will get a new one for $275 and if they don't have it they will give me a new computer of equal or better function. Wow!!!!
On top of that they are sending me a $75 VISA gift card to sweeten the deal. Crazy but true.
So I can get my MB repaired for $200 at my home? WTF am I waiting for? Here's my VISA card #.
Anyway, for anyone who has had the Dell nightmare and no warranty, do what I did and let Dell help. No one can beat that deal on a 4 year old once $3000 SLI 500MB NVIDIA, 1.8TB RAID 0, 2.1GHz Core2Duo, 2MB DDR2 RAM. Hopefully soon I will be back up and running with everyones help and a nice serving of the Dell Service pie. YUM!!!
Thanks to everyone!!!!

If you can't beat 'em, join 'em!

 

[Hemodynamic]

Best answer selected by Hemodynamic.