Alright, so, for some reason, both 7000x64 and 7048x64 have isssues initially booting with my lappy.
When the DVD is inserted, I would have to randomly press a series of buttons that would coax the DVD to give me the option of "press and button..." sometimes this would work, but mostly no.
Only once did it give me the option without me having to randomly press buttons to coax it, out of at least 20 tries.
So, I went into the bios and only let it boot from the DVD - no HD option. It initially gave me a problem ("no OS detected") but then immediately detected the DVD properly, and it was smooth from there on.
Thanks limneos for the help. The USB key worked flawlessly, so it has to be a compatibility issue that Sony laptops have between bios, hardware, and software used. From now on, Im only doing this with USB keys.
So this issue is fixed.