I have an acer aspire. i have an acer aspire one. my web cam is not working. it always says that

Question

i have an acer aspire one. my web cam is not working. it always says that the cpomputer cannot detect the webcam. how come it cant detect the cam if its a built in camera?i cant use it even in the YM messenger.my cousin hae the same model of laptop but she didnt experience the samee thing.what should i do?