You can skip installing 5.50 GEN C, just go ahead and install 5.50 GEN D and then just update to 5.50 GEN D2..

X-dude is correct, you have to put the 550.pbp on the root of your memory stick and the update folder into the "GAME" folder of your PSP..

If you can't figure it out watch some videos online, pretty sure there's tons on youtube that could help you as well..

Goodluck. :taz: