I am reloading Mavericks (clean) onto a Macbook Pro that I have installed a new SSD. I put my Mavericks USB stick in, hold down OPTION and choose it. It loads, and then immediately starts installing, without any intro or welcome screen. Unfortunately, it starts installing to my USB flash disk. Ultimately it errors. I tried it with a 10.8 USB installer, and I get something similar except it immediately says there is an error and it cannot install OSX. At this point, I have the menus at the top and can choose Disk Utility, where I see my SSD and can (and do) partition it correctly. I reboot on Mavericks USB again and it immediately starts installing to the USB. No choice or install wizard. Why??