After plug my hard disk my laptop became slow

Hello,

My laptop hard disk is HGST 500GB sata 6gbps 16mb cache. recently my laptop boot up so slow and i unable to use my laptop since the disk hit 100% in the task manager so thinking that my hard disk might be have problem so i change to another hard disk with same brand and spec. all run smoothly but i want to recover the file from the old hard disk. i plug the old hard disk on the extrenal reader. my laptop detect it but it slow down my laptop when i go to file explorer it only show 2 partition of the hard disk but didnt show to the volume when i try to enter the partition i cant it would stuck there loading. is there any way to get my file from it?