[0x0]

That's for one attempt, right? How often are the nonces found?

[MiWDesktopHack]

The bitcoin algorithm adjusts the difficulty so 2016 blocks are generated in 2 weeks, so a nonce is found every 10 minutes or so.

[0x0]

So every 10 minutes you have a 50% of taking over the chain? If so, sounds like a guaranteed win if you have some time to spend.

[MiWDesktopHack]

Sure, but that just lets you set the next block. You can't use it to generate false transactions because no other client would find those transactions valid.

At best you can drop all transactions that are broadcast to the network and generate blank blocks, thus freezing all future transactions.

[0x0]

Oh, I thought with > 50% you would represent enough "clients" to "prove" the false transactions and earn the trust of the remaining network.