My gateway NV78 laptop starts squealing as soon as it is turned on, not thru the speakers, and continues until Windows is booted up where upon it quits. It runs quiet until it is shutoff and rebooted or turned on. After this started, I replaced the battery hoping that would fix the problem but no luck with that. Do you think the hardrive is going bad?
Most likely, this is the CPU fan. After a while the bearings that support the axle become worn out and the fan starts to make noise, until one day it will stop working. The reason the noise stops when Windows starts is that the speed of the fan rotation can be controlled and it reduces the speed once all the heavy lifting of booting is done and Windows runs. Remedy: replace the fan or wait till it dies and buy a new laptop then. In the mean time I would use compressed air to clean out the duct and heat exchanger so that the fan does not have to kick in that often. B.t.w. when you do some heavy work Video conversion, Compiling, etc., the fan will likely kick in at a higher gear again and start squealing again.