Data Recovery of hard disk after laptop boot

i have decided to boot my laptop yesterday so when i started it , it said it needed an external drive for data transfer or whatever , so i connected my personal hard disk with space 1 tb . Now after the boot is done when i connect the hard disk back it shows up with the name Data E and only has 75 gb of space in which 50 gb has some of this boot related files. I believe that the dish has partitioned GUID and has been used by the boot program . But i am now unable to get into the other partition of the drive . I ahev opened the disk management and found the rest of the space as unallocated and run the wizard to allocate it without formatting and now the rest of the sapce shows up as raw . i have somw important files on that partition. can someone please tell me a way out of this so i can get all my files,HELP?