Hi Janani,
The data you'd resent me regarding the previous registration question is still not the right one. So it is very possible that your woes here are caused by the similar problems.
I would need the epi time series just after 3dvolreg or even before that. The data you sent me is a time series but it looks like it has been detrended already. A detrended time series has no anatomical contrast left in it and there is no way 3dAllineate is going to align it properly.
Lastly, you need to verify that 3dIntracranial is actually doing its job on the anatomy. That program is no longer maintained and we recommend you use 3dSkullStrip instead.
cheers,
ziad