acer aspire won't switch on

[chipmunkmike]

Recently started having a problem with my Acer Aspire laptop. It was working fine one day; the next it wouldn't switch on: it's still the same now. When I attach the battery, it emits a high pitch tone. When I attach the mains, the high pitch tone gets even higher and the machine will not switch on. The power button lights up a little, and so does the caps lock and number lock displays, but the light at the front that signifies power is not lit.
Does anyone have any idea what may be wrong. I guess I'll have to take it in to a shop for maintenance as my warrenty has expired. I just hope that I don't have to pay an arm and a leg to repair something that I have only had about 18 months.
Hope someone can help.
Thanks