While switching my system on,system gives out beep sound!

Does it beep just once? Does the computer have any issues or problems you are aware of?

If its just once and there aren't any issues.
Nothing wrong with it. That beep on start-up means the motherboard has POST'ed, which basically means that its booted into the BIOS. That beep is actually so you can tell the motherboard is working if you don't have a screen attached to see the POST display.

If the beep is annoying you, pop open the case and remove the motherboard speaker.

its beeping twice.......is it nothing serious?

Nothing comes to mind.
If the machine works fine, I don't think there's a problem. The motherboard beep system only tells of catastrophic failures (like bad RAM, bad CPU, missing power cable and such).

Check your motherboard manual, it should tell you what combinations of beeps mean.

thanx for the help

Yea, normally it should beep a single time, however if it still boots up anyway, maybe its just an odd system. What are the full specs of it?

e4500 @2.2ghz,4gb ram,450w psu,msi g41m-p28 mobo,nvidia en210 gfx card

Well the manual for that motherboard doesn't actually list what the beeps mean.

But if this website is accurate (and MSI havent done anything weird with their beep codes). It apparently indicates a POST error.
http://www.computerhope.com/beep.htm

So just look at what the PC displays during startup (before the Windows logo), and see if anything along the lines of an error shows itself.

Nope, that was old IBM BIOS. American Megatrends BIOS is what most motherboards use. Then it indicates a Parity Circuit Failure, which if this website is to be believed, has something to do with the RAM.
http://www.pcguide.com/ts/x/sys/beep/amiB2-c.html

Check in Windows if the full 4GB of RAM is detected (go to "Computer", should say at the bottom). If it is, no idea whats wrong then.

it just shows up the motherboard model and starts up