First things first, in order to have anything on a drive, ie: data or an operating system, you have to have partition(s). Next, have you already installed XP on the first drive or are you still trying to get the bios to see two drives? The boot.ini file has nothing to do with recognizing the slave drive...it is only used by XP to determine where it is installed so that it can run.
I'll assume you have XP already installed on the first HD and you're trying to add a second drive. You're problem lies with the slave drive. First, do you know for certain the 2nd HD works, have you tried it by it's self? Does the bios see the 2nd drive? If so then does the 2nd HD already have files on it? Has it been partitioned and formatted?
Please provide some more info so that someone can help you.
Cheers