If it doesn't say bootable after the ISO9660 bit then the disc isn't bootable. You'll need to edit the ISO image with another program to add the boot image, or if you want to use only ImgBurn, you'll need to mount that ISO to a virtual drive.
Try burning at 4x or 6x. If that doesn't work, try a lens cleaning disc on that drive.
You could get better quality burns if you used high quality media such as Verbatim and Taiyo Yuden blanks.
Test Mode doesn't actually burn data to the disc. Also the media you're using is write-once, not rewritable. Try again with Test Mode disabled and it should work.
If you have an Audio CD and want to make a copy of it then follow this guide -> http://forum.imgburn.com/index.php?showtopic=6380
If you have MP3/AAC/FLAC/WV/etc files and want to make an Audio CD from them then follow this guide -> http://forum.imgburn.com/index.php?showtopic=5555
No two discs are exactly the same, the quality can vary even in the same batch: that's why the burner makes small adjustments on each burn to make the burn quality as good as possible, but it can't work miracles.
You get what you pay for.
If ImgBurn said there's not enough space then DVD Flick may have created an image too big to fit on the disc.
You can disable the "create ISO image" and "burn with ImgBurn" options in DVD Flick's settings, then you can use ImgBurn to manually burn the VIDEO_TS folder generated by DVD Flick (look in our Guides section).
Also make sure you have the latest ImgBurn version.
Update your burner's firmware (remove any disc and close the tray before updating then reboot after it's finished) and try again. If it doesn't work at first, do a Full Erase before trying again.
If all that doesn't help then you'll either need to use a write-once disc or buy another rewritable disc (Verbatim brand highly recommended).
Update your burner's firmware (remove any disc and close the tray before updating then reboot after it's finished). Try burning at 4x. If that doesn't work, then try a lens cleaning disc on that drive.
If all that doesn't help then please read this -> http://forum.imgburn.com/index.php?showtopic=8000
Wii game discs are protected and, not only ImgBurn doesn't copy protected discs, but most drives aren't able to read Wii game discs.
Have a look around with Google and you'll see what I mean.
Their P33 BIOS is already in bootable ISO format ready to burn:
http://www.bfgtech.com/CMDocs/BFGTech/691N1P33.iso.zip
Isn't this what you're looking for?