Here is a list of what's happened so far:
Ran a Super AntiSpyware scan.
Tried to re-boot computer but it would get to the Welcome to Windows screen - wait a minute or two, and then start re-booting.
Going back to last known configuration did not work.
Safe mode got to welcome to Windows screen but then went into re-booting as above.
Eventually used the HP Recovery Disks to get laptop to boot - back to August 2006, but hard drive working fine.
Used file recovery software to save everything to an external hard drive (I have a Windows Live OneCare backup from a couple of months ago, which I plan to use and then update that from the newer 'lost files'.)
So plan is to format C: drive and then re-install Windows and all other applications.
Booted PC into Windows and ran chkdsk /r
Plan was then to re-format hard disk using the Windows XP disk Recovery Console.
Set Up loads OK from the XP disk but when I press R it comes up with 'Set Up did not find any hard drives installed in your computer. Make sure any hard drive disks are powered on ... etc. etc
I then tried re-booting to use Set Up and it came up with 'Windows XP has not been set up on this computer... etc.'
I tried booting the PC and using CMD to see if I could format the drive from within Windows but got the following:
'Format can not run because the volume is in use by another process. Format may run if this volume is dismounted first. ALL OPENED HANDLES TO THIS VOLUME WOULD THEN BE INVALID. Would you like to force a dismount of this volume? Answered Y and got the message:
Can not lock the drive the volume is still in use.
So my XP installation disk is not seeing any hard drives so I can't re-install Windows or do anything at all using the disk, yet the hard drive is there and working as I can log in OK. I am now really stuck.
Anybody out there have any clue as to what's caused this, what's actually wrong, and more importantly what I can do next?
Cheers, and thanks for anything you can offer on this one.