What is it?
Creative CD Assistant Service - CTSvcCDA.EXE

What does it do?
CTSvcCDA.EXE - This is a service creative by Creative labs to help your CD drive. Every time you insert a CD Creatives Player will try to play it for you. I suggest removing this and using either the built in Windows Media Player or Winamp.

Virus Precautions:
You'll want to keep an eye on this google search for any known viruses. The normal location of this file is C:WINDOWSSystem32CTSvcCDA.EXE