I am using a usb drive but when i load wbfs file from wii flow it shows a black screen. When it shows the black screen I hear the wii disk drive making noises. Why is this happing? It worked a day ago.
"using a usb drive"
There's the problem.
If you're thinking "but it worked yesterday" that's the way she goes with flash drives, they are shit and will stop working, as you can see.
External HDD is the only way to go about playing backups on the Wii.
For me if you want to emulate the DS the best option is on Android, use DraStic and a controller that holds your phone... it's clunky but it works insanely well. The next best option in my opinion is using a New 3DS XL, not really emulation but hacked it works really well.