I have a client who owns a Sony Vaio desktop. After the machine has warmed up it emits a high pitch whistle and the on/off switch flashes between orange and blue. At the same time the computer slows down. It's particularly bad when the computer is working hard - but this problem exists even when the machine is just running Word - and it's worse in hot weather. Sounds like an overheating issue but interested in anyone's opinion and suuggestions.There's enough RAM 512Mb. Phoned Sony, but this drew a blank (hah!).