Every time I try to run a game the computer stops, up comes the blue screen with a message saying that KMIXER.SYS has caused this shut down, has anyone else experienced this?

Has anyone got a solution or any possible causes

KMixer system driver (kmixer.sys), is the kernel audio mixer.

You may want to do a "SFC /scannow" from the command prompt to see if your
kmixer.sys is corrupted.

Also can you supply the complete error message?

Also: look in your event viewer: rt. click My Computer then click Manage then Event Viewer.
Open the system as well as the application tabs & look for X errors. Click error line for details. Post back the source & event id especially of errors that seem to coincide with a crash.