How to use case in MSSQL 2005?

Hi

I have a select query which needs to take clientid as where condition. However, if the clientid=0, then it needs to select all result.

Select * from client where type=1 and clientid=2
 
if clientid=0 which I pass it from C#
then
Select * from client where type=1  //and clientid=0 would be taken out
 
I tried:
Select * from client where type=1 
case when (t.clientid ='0' then '' when t.clientid <> '0' then and t.clientid = '2') order by [id] desc
 
But, it said Incorrect syntax near the keyword 'case'.

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