HI,

I've managed to successully unlock my 550.

Gigabyte GA-MA790XT-UD4P (F4 Bios)
550 BE - AC098BPMW

ACC - Hybrid/Auto (-2 all cores)

4GB OCZ 1333 Platinum @ 7-7-7-20
Titan Fenrir
Antec 300 with 4 fans

Havent had a chance to stress test properly or overclock as it was getting late last night but will try to have a go tonight. Was sitting at 35c in BIOS when unlocked at standard clock.

I have installed Vista x64 SP2 and GTA4, played that for about 1 1/2 hours as I wanted to test my 4870 as well before I hit the hay, went without a hitch. All looks sound so far but guess I won't know for sure until I stress it.

Will post some screens when I get a chance.