I wish to save a text file to the client system.i had try ed in my desktop its working fine when i run from server its showing error
this code i had given and each client system there is a folder name FCR.
fs = new FileStream("d:/FCR/FCR" + strdt + ".txt", FileMode.Create, FileAccess.Write);

please help me ..

I'm not sure how your "web application" is deployed and you cannot simply access the file system on a client from a web service, but I won't make assumptions since you indicated you have "FCR" folders already setup on the clients. Try adding some exception handling around your file IO: FileStream Exceptions...

are the files definitely on the d: drive on the clients?