Ahh if windows is the second partition, and wasn't before partition magic, they you have to trick windows into thinking its still on the first partition.
map (hd0,0) (hd0,1)
map (hd0,1) (hd0,0)
If root(hd0,0) worked for you then it maybe that the bootloader is still there and wasn't moved by partition magic.
Some Distros don't put the ntfs module into Linux by default ( as its considered experimental and dangerous ). Theres porblems with writing to ntfs disks. Try adding it ( one of the redhat-config programs probably does this ).
If this doesn't work move your swap to the other end of the disk ( which is a better position for it anyway. ) and move windows to the front again.
Never used partition magic so I can't help with that.