nearly 700 movies each will run for one and half an hour. to store it how much memory is needed in a hard disk? or any other device have the capacity to store?
No, you will not need that much space. You should be storing them in a compressed format (such as H.264) which means they should take up about 700 MB each.
Total Space needed:
0.7 GB * 700 = 490 GB
I would recommend going with at least a 750 GB hard drive to store your movies.