|MSI mboards are well known to be more likely to have this problem.....|
Some mboards develop this problem - electrolytic capacitors were installed on them that were not properly made, and they fail eventually - the mboard manufacturer didn't know they were improperly made at the time the mboard was made.
Open up your case and examine the mboard to see if you have bad capacitors, and/or other findable signs of mboard damage .
This was the original bad capacitor problem - has some example pictures.
History of why the exploding capacitors and which mboard makers were affected:
What to look for, mboard symptoms, example pictures:
Home page that site
- what the problem is caused by
- he says there are STILL bad capacitors on more recent mboards.
Pictures of blown capacitors, other components, power supplies, fried Athlon cpus, etc.:
The noise you heard was likely one or more electrolytic capacitors exploding.
I happened to hear one explode once and it sounded like a muffled rifle shot (the computer cased was closed). In that case it was inside the power supply, but it was caused by the same thing.
It's also possible for them to cause shorts while failing , if the aluminum enclosure they're in touches the two leads inside the capacitor, which may explain the sparks you saw.
How did you see them? Was your computer case open at the time ?
Unfortunately, shorts can damage anything connected to the mboard or to the power supply.