so the loud computer sound that woke me up the other night was definitely a fan noise. even worse, that "siren" sound came back before long. it seemed awfully strange that i was having more fan trouble already, but the last time we'd opened the case we'd noticed that i didn't have very good circulation in there, so last night we went to compusa & bought some new case fans to install.
once we got home & opened the case again, barry discovered that the brand new heat sink i'd bought last month had already broken. there was even a big crack in the fan! i imagine the sound that woke me up was the fan itself cracking. what a hunk of junk.
fortunately, when i went back to compusa today, they gave me no hassles exchanging the broken heat sink, even without its packaging. i also exchanged one of the case fans i'd bought yesterday: i needed one with a different adapter. however, the only fan i found that was the correct size and had the correct adapter at the correct price turned out to be one of those tricked-out bling-bling fans with LEDs in them.
barry installed all my new fans & things are working fine again, with better circulation than ever before and a faint green glow coming out the bottom.