Yes, you need to overwrite (AFTER having made a BACKUP, and IF you are sure you have an alternative way to boot the machine), the following two files:
NTDETECT.COM
NTLDR
(you can get them from any already installed XP, and, if I recall correctly they are even between the files in SP2)
I have read some reports that the files must be in the SAME language than the original install, but I cannot confirm it, italian and english mix well, cannot say for other languages.
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“The Government of Spain will not applaud those who set the world on fire just because they show up with a bucket.” - Prime Minister of Spain, Pedro Sánchez
For my 2000 install it doesnt really take that long to boot up, I will time it the next time I boot. I would say about a minute or so. And even then I just leave the room while it boots up.