Classical repair boot operations
Fix the MBR: fixmbr
Fix the partition boot record: fixboot
Fix the boot menu
cd c:\ attrib -hrs boot.ini copy boot.ini boot.ini.bak del boot.ini bootcfg /rebuild
Determine Windows XP version
From dos prompt or recovery console, assuming c: is the windows installation
type c:\windows\system32\prodspec.ini
Will give you something like
(...) Product=Windows XP Professional Version=5.0 Localization=English ServicePackNumber=0 BitVersion=40 (...)
This however doesn't give the XP SP version.
Determine Windows XP Service Pack version
From Recovery Console, while in the Windows folder type:
dir explorer.exe
The date and size will tell you the Service Pack installed:
NoSP = 08/23/2001 05:00 AM 1,000,960 explorer.exe SP1 = 08/29/2002 03:41 AM 1,004,032 explorer.exe SP2 = 06/13/2007 03:23 AM 1,033,216 explorer.exe SP3 = 04/14/2008 05:42 AM 1,033,728 explorer.exe
Check important system files
Assuming the recovery console has the same XP version and service pack than the one installed on disk, you can do: Sfc /Scannow
There are however many wrong alarms with that command.
Error while loading system
If you still get something in the lines of "Erreur lors du chargement du système d'exploitation" after fixing the mbr and the partition boot, there might be a hardware failure going on. I got a case where a 250 GB hard-drive was installed on an old motherboard. Only 136 GB were detected, but more importantly, the bios HD recognition was set to Auto. You may want to check that LBA (Large Block Addressing) is enabled and not "Auto".