pag boot mo, press F8, there will be several options there, check if any works (i.e. safe mode, repair your computer, last known good configuration, etc)
kung before pa lang dun, lumalabas na yung boot manager, the other option would be to do a repair install by using the windows installer
also try to do checkdisk and surface scan on your old HDD, baka nagkaron lang ng bad sector and natama dun sa boot file