I just downgraded my PSP from 2.0 to 1.5, but in the middle of doing the downgrading firmware (I was at 90 percent) when it said updating failed and I need to see Sony technician. It reset itself and I was glad to find it's firmware was 1.5... I got some Homebrew progs working as well as my Sampler disc working just fine, but Im still wondering if there was any damage in the firmware... There's no such thing as a partially damaged firmware is there?
