did you use a meat thermometer to see if the center of the laptop was 350 deg and safe for eating???
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on old laptops could be one of the ram sticks is lose...or the hard drive is going bad. a lot of time slow boots into window is system with a lot of programs in start up and low memory. another issue can be a virus and or more then one anti virus installed on the pc. what I would do is make a cd or usb stick of hirem boot disk . on it is a mini xp boot see if with a clean usb or cd the laptop runs faster. if it still slow slow...ckeck to see if the cpu fan is clean and working...broken cpu fan...cpu runs to hot and has to slow down so it wont over heat. I would google your model and class action lawsuit. a few of the older hp...