Yes, you will need to give the "System Reserved" partition a drive letter before you can browse its file structure, and copy the "ntldr" and "ntdetect.com" files into the root of that partition.

To do that, go into Disk Management (if you left it, that is

), select that partition, right-click, and you should see an option to give the partition a drive letter. Pick any one you want, and once you're done doing all that, XP should boot.
EasyBCD modifies the boot.ini file in your "system" partition, so yes, that will be the boot.ini its updating.
Jake