What to do when missing NTLDR and Hal.dll ?

The simplest thing to do to try to resolve this is to start with XP's Rebuild command. The short form of the fix is as follows:

Step 1. Boot from your XP Setup CD and enter the Recovery Console
Step 2. Enter the command attrib -h -r -s c:\boot.ini
Step 3. Delete the file (del c:\boot.ini)
Step 4. Run bootcfg /rebuild
Step 5. Run fixboot

Those five steps can fix a number of thorny startup issues and may be all you need.
But if the above is too telegraphic for you, you can read fully detailed instructions in my InformationWeek article, "XP's Little-Known Rebuild Command."
http://www.informationweek.com/LP/showArti...&queryText=
Microsoft's official instructions can be found in
"Description of the Windows XP Recovery Console"
http://support.microsoft.com/kb/314058/en-us
and "Recovery Console Tools and Settings."
http://technet2.microsoft.com/WindowsServe...3.mspx?mfr=true

If the Rebuild command doesn't help, you may be able to solve the problem by attacking each error message separately.
For example, Kelly Theriot's excellent site has a very complete how-to on the Missing HAL.DLL problem.
http://www.kellys-korner-xp.com/xp_haldll_missing.htm
Also, Microsoft offers "How to troubleshoot the
'NTLDR Is Missing...' error message"
http://support.microsoft.com/kb/318728/en-us
and " 'NTLDR is missing' error message when you install or upgrade Windows XP."
http://support.microsoft.com/kb/314057/en-us

Finally, if none of these software fixes work, or if the problem comes back, then indeed you may have a subtle hard-drive problem. It may be related to a marginal power supply, a heat issue, or simple old age (i.e., the drive's actuators are wearing out and functioning erratically).