my computer makes a wierd beep

[FearThePenguin]

my computer makes this wierd sound. it comes from inside my computer. its hard to explain what it sounds like. its not realy a beep, its more of a highpitch soft sound, folowed by a click, then a wierd beep. its realy weird sounding. its been doing this for a long time. of course i only notice it when i am around it so i dont know how many times it does it a day, but it seems like it only does it once a day late late at night. like 12am-3am. thats when i notice it. it doesnt have an exact scheduald time. also, it did it before my reformat. it seems to do it every day but i cant tell. i dont stay up and listen for it. what could this sound mean?

windows 2000
A7V266-E
athlon xp 1800
geforece fx 5600

 

[GreenApe]

What kind of hard drive do you have by chance? My hard drive seems to make a noise every night during those times too... sort of eerie...

 

[FearThePenguin]

i forget what it is. but it sayes falure may be immenant when i boot up. dunno if that has anything to do with the beep