winsys9x.dat definition, relationships, removal:

This is a part of a malicious parasite that violates user privacy and damages the compromised system. The winsys9x.dat file can be used for different purposes depending on the related parasite's type, functionality and carried payload. Although winsys9x.dat may not take any malicious actions by itself, it ensures that a parasite is working properly and therefore needs to be removed. DO NOT open, execute or edit winsys9x.dat!
The winsys9x.dat file is installed and used by keylogger Diablo Keys.
In some cases a presence of winsys9x.dat does not mean that your system is infected. The file may actually belong to some fully legitimate applications and therefore must stay intact. If you are in doubt, please scan the winsys9x.dat file using you regular spyware remover or antivirus program.