Click the "Disk Image" radio button, then click on the button with the "..." and browse to where the Memtest86+ ISO is. Select your flash drive's drive letter from the drop down box next to Type: USB Drive, then click OK.
You shouldn't be getting a kernel image problem when you run the auto-installer. Did you pick the option to reformat the flash drive when installing it on there? Are you sure you're booting off of the correct USB device?
Found out I didn't need Unetbootin I just needed the memtest and boot it from BIOS. Ran memtest and no errors after one pass then I bumped the wrong button and the computer booted on Windows. Still registers as 1GB of RAM.