mine beeps like that if my ram timings are too tight, or overclocked too far.
but it hangs when voltage is too low.
what is your voltage now? if it is stock (1.35 i think), then by all means raise it up.
i would up the cpu voltage but not too much past 1.5-1.55
i would suggest not going over 1.625 ever. i have done that voltage before to see how high i could post, but temps were no good....scary.
if it doesn't post at 2.6 with 1.5 volts, you've got something else going on.
mine posts at 2.75 with stock voltage, it just isn't stable.
can you post a screen shot of your bios?
EDIT: also, i don't know if that calculator thingy is correct, it does not let you figure ddr2....
but the definitions and advice below it have earned a spot in my favorites...!