Acer/eMachines E640 notebook beeps when left in sleep mode

Hi everyone, i was looking for help with the problem in the title when i stumbled into here and saw some of the excellent help people were reciving. So i decided to register and see if anyone could help me!

I was in desperate need of a Laptop after i was set upon, stabbed and robbed last year, very sad.
Anyway, i didn't have much spare cash but once i had sufficently recovered, i went looking for a decent budget laptop.
I managed to get this one for around £200 which i thought was a good deal.
It's specs; cpu:Athlon 2 x2 P320 2.1ghz, video: ATI Mobility Radeon HD 4250, 2gb DDR3 ram (which i upped to 4gb), 15.6 HD LCD screen, 250 gb HDD and a DVD Re-writer.

Now to the problem. If it has been left in sleep mode for a while it starts making a beeping sound. A single beep every 1-2 seconds. On closer inspection it sounds like something trying to start spinning, like the HDD, the optical drive, the fan etc, but why would anything be trying to start in sleep mode?

I have been meaning to do something about it, for the longest time, but when i'm using sleep mode i'm usually going away from the Laptop for a short time, or going to sleep for a while, so i don't notice it till i get back or wake up. And since the Laptop seems to be working it just goes out my head.

I am determined to get to the bottom of it now though! It's in my mind at the moment and it's staying there till fixed!
Any help would be most welcome.