Crazy ass computer question (cooling freaks)

[Rockstone]

I have a SFF - small form factor box called an ice cube.
In it is an ATI X700 video card.

There are fans on the CPU, Chipset, Vdeo card, Case exit and PSU.

Here's the crazy part. I hear this sound that sounds like a bomb dropping. It comes from the inside of the computer,

Its about 2 seconds of a series of falling tones followed by an explosion sounds.

What the F is that? is the motherboard trying to tell me something?

[sir_captain]

1. If I had to guess

I'd point at the PSU

Most PSU's are cheap and suck and make lots of noise. Hard drives, though without fans, are often the next culprit in the making too much noise category.

I'm about to build a new machine and I've had it with loud computers--I'm making it a goal to have a completely silent machine. I'll use acoustic paneling, hard drive sleeves, special fans, the whole shebang.