My advice is that you check for all causes that could be slowing your lap, may be don't need an hdd change, sometimes even a defragment can help, os change... micro too hot, memory amount... tooo many causes.
i have a dv6000 and as many times i clean the fan and all the dust inside. once assmbling it, accidentally caught the touch pad ribbon with one of the screw that goes besides the wifi adaptor. now i cant enter any os that uses mouse, it looks like the touch pad control is burned, keyboard works fine and everythig else works fine, msdos fine, just no windows or linux, they stop boot in the exact moment it have to check for mouse. what can i do? any body knows? please help.