It is a component of malware or spyware, you should immediately remove it using an antivirus and antispyware program. If that does not help, then ask us for help in the Spyware removal forum.

Name: wdmaud
Filename: wdmaud.sys
Registry key:

[HKEY_LOCAL_MACHINE\software\microsoft\windows nt\currentversion\drivers32]
“aux2″=”wdmaud.sys”

Command: C:\Windows\system32\wdmaud.sys
Startup Type: Sound drivers
Description: C:\Windows\system32\wdmaud.sys is a trojan/Google redirect also known as Rootkit.Win32.Agent.fwt. The legitimate wdmaud.sys actually exists at C:\Windows\system32\drivers\

How to remove: use the instructions How to remove Google searches redirect virus 7.7.7.0 (remove Rootkit.Win32.Agent.fwt)