it is highly likely that the mbr is still on the slave drive and therefore it will still cause problems even when jumpered as a slave. disconnect the old slave and only use the drive you have designated as your master for a few times (as per " Patio's " instructions) the mbr could be changed during use as the master, then after a few boot ups try with the slave drive attached.
or
do a repair installation!
or
it could be fixed using fdisk /mbr if you know how to make a windows floppy, but this all depends on if you have any partitions on the drive, normally fdisk is done during the installation of XP and you will not even see it happen. if you have no partitions there is really no problem about using FDISK /MBR.
Look at this for a guide.
http://support.microsoft.com/kb/69013fdisk /mbr can be done from the recovery console
or
please note the FDISK for XP is different from other versions of windows, you can create a floppy by going into mycomputer then put a floppy in the drive and format the floppy as a system disk.
if you have anything important on the drive you now want to be the master then back that datra up, do a repair installation and the problem should be resolved