So I know my Dell Inspiron 1525 is probably on its last leg. But today I have been noticing this sound coming from it every now and then and I'm just wondering what it is. It sort of sounds like the disc drive spinning but there isn't a disc in. Is there a scan or something that I can run? The O/S is Windows Vista.

If you hear what sounds like a mechanical scrapping noise, it is most likely bearing from a motor - either a drive motor or a fan motor. Either can spell trouble. If your hard drive bearings are failing, you risk losing data. If fan bearings are failing, you risk overheating and losing data. So you can try blasting cleaning all the vents and cavities of dust, but it might be better to a shop take a look. And in any event, I would backup any data you don't want to lose - now.