Drive:\Boot\Bootsect.exe ?NT52 All

Note the hyphen instead of the slash. I haven't tried it with the command you found but I can confirm that the above works.

Also, it's important to note that if Vista is installed on the primary partition, deleting or formatting that partition will likely render XP unbootable until you perform a repair installation. (All of the boot information is stored on the single primary partition.)

Aside from that it looks like you're good to go.

Good luck.
John