
This is what you wrote on your 1st comment.
If you meant to ask about how to play your disc copy of
SSBB, then why did you mention
Legacy XP?
Anyway, if you're having trouble launching the iso of
SSBB from
usbloadergx you should've said so. You should verify the iso file, do that in
WiiBackupmanager, it's under "tools" in the top banner.
Also, depends if you ripped the game yourself or not, it's most likely corrupted if you're using a fat32 partition in your usb flash drive (where the iso is stored).
I would suggest ripping it again, do it in USBLoaderGX, it has the option to do on your drive.
And no, Wii isos are not read by the disc drive.