Do a google on how to do a repair install to get rid of the NTLDR error.
You cannopt turn your system and second HD into 1 drive without formatting and setting up a RAID-0 array. Also, your IDE/SATA controller needs to support it.
I would suggest you resize your current XP partition using Partition Magic and create a 2nd partition on driveA. Then use XP's dynamic drive feature to setup a software raid config using the 2nd partition on driveA and the main partition on driveB.
Only available in XP Profesional.
TheMajorMMX - Intel P200 MMX @ 225Mhz - V-Tech (PcPartner) Baby-AT mb w/ Intel Triton TX chipset - Nvidia Riva TNT2 M64 w/ 16MB - 256MB M-Tec SDRAM - Still running.....