Identify WFE Vs Complete option used

Refer http://technet.microsoft.com/en-us/library/cc262901.aspx

“You must use the Complete installation option on all computers you want to be index servers, query servers, or servers that run Excel Calculation Services.”

To identify which Sharepoint Server is installed using complete option, just check the Excel Calculation Services Tab is available in the Services on the Server.

To Change a server with WFE to Complete, follow the following steps

1. Remove Server from the Farm

2. Uninstall Moss

3. Install Moss with complete Option. Install the updates(e.g., SP2)

4. Add to the Existing Farm.

That is it.