antiak.sys (aka 'AK Service') is a leftover device driver from some anti keylogging software or some such. It goes out of its way to hide itself from you and does not get removed when you uninstall the software(!). antiak.sys is known to cause crashes and instability on Windows XP and likely any other supported OSes, usually resulting in untimely BSODs.
There is hope! Here is a removal tool: antiak-remover-0.1.zip. Please read the readme.txt before attempting to use. Enjoy!