hack into a windows PC with no password

What you need is a computer/laptop with Linux, connect it to the to-be-attacked PC via a firewire port and need to get the tools from this site. Run a command and voila! The attacked PC is tricked into allowing the attacking computer access to its memory. With full access to the memory, the tool can then modify Windows' password protection code, which is stored there, and render it ineffective.

On the flip side, make sure when you're not using your pc (and it has firewire port) disable the port... under My Network Places->Network Connections. Disable by right-clicking on the 1394 connection.