if You purchase a HP laptop and under its warranty period you find some problem with its harddisk, does HP allow you to just send the harddisk or do you have to send the whole laptop?

Background:-
I had purchased a HP laptop , it came with 160 gig maxtor harddisk,I upgraded my harddisk to 500gig (western digital ) ,and started using HP's (maxtor) harddisk as a 'usb' via a USB case .
Now the HP's harddisk is showing read/write errors/badsectors so If I contact HP will they ask for teh whole laptop or just harddisk?

I am asking this so I am 'prepared' when I call their local office.Here these multinational offices act very arrogantly (and unfairly/justly/ethically ) and I am in another city, transporting a buggy harddisk is safer than transporting a precious laptop plus what will I do when they keep the laptop to replace the harddisk when infact the problem is just with hardidisk?

maybe you should try to fix the harddisk first
try a lowlevel format
could be the filesystem went bad

Not sure about laptops, but with desktops, HP let my parents just ship the hard disk. Of course, they don't do any data recovery (even though it was a known issue with this particular model Seagate) and the fix was relatively easy and would have resulted in zero data loss.

I will bet you that HP claims you have voided the warranty by removing the HD and putting it in an external enclosure.

There might even be merit to the argument, if the drive was dropped or subjected to excessive heat or vibration.

no drive was not dropped or subjected to excessive heat or vibration.
yes i replaced it but wont that classify as a simple system upgrade?