Installing NAI GS4.5 On Cluster ExchSrv

Can any buddy guide me on a way to install NAI Group Shield4.5 on a cluster Exchange Server?
I’m using Exchange 5.5 SP3 that i updated later to SP4, on a 2000 advanced server platform.the data is stored on a shared storage not locally on the server.
when i was installing the GS, i reached the window that asks me to specfiy the name of the sever and the location where the software is going to be installed which i changed it to the shared drive where the exchange is located in, it gave me an error saying that i should specify the shared path where he exchange is located in????
has any buddy faced any thing simmler to this problem? if yes i would be greatfull for any one how can help me.
thanks