Dell Studio 1555 Windows 7 Home Premium Sudden Beeping

So yesterday I was busily doing some work and watching something on ITV Player when shock crashed along with Microsoft Office 2007. From nowhere it started continuously beeping at me. It was rather high pitched and didn't sound as though it were coming from the speakers. I flipped it over and had a listen and it sounded as though it were coming from inside. I switched it off and back on again but the beeping simply started up again. Continuously beeping for maybe two minutes of so, frozen on the Dell start up logo, unable to enter either boot menu. However after about five mins, i received the message:

Operating system not found

i tried inserting my windows 7 disk to do a clean install but no drivers were found. I shut it down and unscrewed the back, turned it on and had a listen. It sounded as though the hard drive was beeping, but i didn't think it even had a speaker, so Im assuming whatever is beeping is because of the hard drive. I took it out and reported the.laptop, same results as before but without any beeping at all and a much faster boot time. So my question is...what is wrong and what can i do about.it? Thanks for all the help, this laptop is only 3 years old and really i don't want to be getting a new one soon. Thank you.

Well i think when i counted i reached 220, so its quite a substantial amount before it stops. All evenly spaced apart by about half a second each.