External hard disk not recognise and makes the whole computer sluggish

Hi, I have a Western Digital WD 1311B, and when I try to connect to my Macbook Air, it is very slow and causes my whole Macbook to be sluggish to the point i just had to restart my whole Macbook. This hard disk works on every computer apart from this one. When I try to load Disk Utility with my hard disk plugged in, it will just keep loading untiI I plug out my hard disk. Same thing happens if I try to reboot my computer with my external plugged in, it just won't load until I plug out my external hard disk. The format of this disk is exFAT. I had contacted Apple Support, but nothing seems to solve my case. I had tried:

• SMC Reset
• Reformating hard disk
• Disk utility
• Going into safe mode and disk utility (This method didn't work disk utility keep loading)
• Switching users (I saw my hard disk in Finder but when I tried to create a folder, it crashes, and my external hard disk won't be visible.)
• Finder-library deleting series of folders that Apple Support suggested me.

Any suggestion would be greatly appreciated.

Cheers,

Jeff