I found a great little utility for measuring temp whilst in windows a while back... I'll see if I can find the link.
Hmm. I can't find the page, but here's the link to the FTP site:
http://mbm.livewiredev.com/download/MBM5191.EXE
You'll need to configure it yourself, but it gives a complete rundown of the system functions your mobo supports...
Tell you what, I'll do a screenshot for you...
If the beep is coming out of your soundcard though... it doesn't sound like a temp problem. Your BIOS handles the system temperature, so if there is a warning it should come from your system speaker (since your BIOS doesn't know how to make sound come out of the soundcard). Unless you've got something else to monitor your temperature. I dunno.
: goes off to google stuff :