The fuse/s for the radio are located in the fuse box under the hood. Check your manual.
I only pulled one fuse (don't recall which one) and I didn't loose any settings on the system.

Pop the hood, mid-back right hand side.

Radio 1

Ditto on the fuse, worked for me. I think it's #15, pulled it for about 2 minutes and there is a super handy little fuse pull tool attached to the underside of the fuse box cover. Thanks Toyota!

The only fuse you need to pull is under the hood. I can't remember the number, but the fuses are clearly marked on the inside of the cover. The fusebox is on the right hand side of the engine compartment.

SUCCESS!! thanks so much to all of you for your savy. after three failed attempts, i finally made my hybrid nav dvd on my iMac G5 after downloading a program called dragon burn (reccomended by a co-worker) and taking advantage of the free trial version. i inserted the burned dvd into the nav, up popped the map with my current location. i tried the override, no luck. so i removed the fuse and reinserted it after a few minutes, i tried the override again, and volla.

btw...it's not fuse #15, it's a 15 amp fuse. thanks again. i couldn't have done it without you!