[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.