The problem is not due to the fan. As you have mentioned that the problem existed before.
Thou its a good idea to change to the original fan ..but any other fan which works fine should not be an
issue.
Sound like you problem could be related to software or possibly a virus. Could it be that the audiodg.exe
has been compromised.
In addition to your anti virus, run spybot and adware. Also try running free antispyware from
http://www.superantispyware.com/Good luck.