never had to erase anything, I used the PRO hotspot selector, selected my ssid (be sure to be within range of your router whatever) turn iso cache off and high memory output (I think that's how it's called) on on the recovery menu under advanced, and done about iso/cso... dunno
right get a mgs pw ISO then we schedule a match to test the client.
download that tool, select your hotspot
and head to the recovery menu, advanced, iso cache off; high memory on, reset vsh
hope I helped
sent using my PSP 2004