Hello, we are trying to establish a parallel programming environment using mpich2. [Specification of our environment] OS: Windows 7 (64bit) Two workstations: Intel CPU (64bit) Programming environment: Visual studio 2008 (64bit) We have two questions regarding mpich2 installation. We have tried 64bit mpich2 (version 1.4.1p1, 1.3.2, 1.3, 1.2), but all of them give an error message ("MPICH2 not installed or unable to query the host") in the wmpiconfig program. Also, when we click scan hosts in the wmpiconfig program, the items in the list of hosts are in gray which means error occurred. However, we could successfully execute a parallel program with 64bit mpich2 (version 1.3.2) on the 64bit machine even though this version still shows the error message Q1) So, we hope to know that we may simply ignore the error message. On the other hands, we experienced that most of 32bit mpich2 versions (version 1.4.1p1, 1.3, 1.2) work in our environment without any error message. Q2) Is it fine to use 32bit mpich2 on a 64bit machine? We hope to know if there is any disadvantage on this such as performance degradation. Thank you. Best regards, Seokho Son.