If you live in the London area I might be worthwhile popping down to HMV Gamerbase at London’s Trocadero Centre where you can attempt to hack (guess a 6 digit number) their Bioshock 2 PC to win it. It's a custom built beast of a gaming PC assembled by the 'performance specialists' at Scan Computers. Specs below. You are apparently allowed one attempt each per day.

Intel Core i7 870 (Overclocked)
Asus P7P55D motherboard
Corsair Obsidian Chassis
Corsair H50 Cooler
Corsair 550Watt PSU
Corsair 4GB TwinX memory
XFX GTX285 NVIDIA graphics card
500GB Samsung Spinpoint hdd
DVDRW
Windows 7
Internal blue lighting