Hello Ibrahim,
Windows computer tries to authenticate using both machine and user credentials (these settings can be changed in the advanced parameters of your authentication tab on the network adapter setting on your machine).
the attempt with host/ just indicate that the computer tried to authenticate using its machine credentials.
to test if AD and ACS works fine, you can use this command on a switch that is configured to auth through AD via ACS:
switch#test aaa group radius USERNAME PASSWORD legacy
It should return a sucess.
Hope this help,
Bastien.