It may be a problem with FAT32. Try these procedures: http://support.microsoft.com/default...b;en-us;314057
If you have just installed XP, you may want to format and reinstall using the NTFS
file system. XP is more at home with that.
If it is a file-system issue, problems could arise later, too.
A fragmented MBR with ntldr in the second fragment will also cause it not to be found, but that isn't possible with FAT32.
You might try fixboot and fixmbr from the Recovery Console. Boot from your CD and choose the Recovery Console. Once logged in, type: Help for a list of commands.
Try chkdsk from the console. Type: chkdsk /? for options.