I Think My HD is Dead!!

Hello all!!

Lately my HP Pavilion ze4427wm's HD has been acting up. When I want to run Disk Defragmenter, it always tells me there is some kind of inconsistency with the HD and I need to run CHKDSK. Well I do and when I restart the machine all is fine until when I want to run it again, it asks me the same thing. I re-formatted my laptop a couple of weeks ago, and I just installed Windows XP Service Pack 2. When I did, I got a message telling me you need to insert your Windows XP CD and repair the Windows installation. I try doing this, but every time it asks me for an administrative password, even though I don't have one. So when I re-boot the machine, it sits on the desktop for about 3 minutes and then prepares to load. The Windows taskbar won't show up on the screen, but all my applications work. HP's BIOS includes a HD Self-Tester. I just ran it and it failed. My guess is that the HD is toast. Can anybody back this up? The computer has been acting wonky for about 6 months and now it can barely boot up. Thanks for the help!