No, you can't simply put desktop computer's hard drive in a laptop. Desktop computers and laptops use different size (in physical dimensions) hard drives. Desktop hard drives are normally 3.5 inch hard drives, while laptop hard drives are 2.5 inch. Looks like $50 is going to be about the minimum cost for a hard drive for your laptop; see
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You also need to determine whether you need an ATA or SATA drive. If you tell us exactly what model laptop you have, someone should be able to help with this determination.