This paper studies relay amplifying matrices and transmitter/receiver beamforming vectors of the amplify-andforward (AF) multiple-input multiple-output (MIMO) halfduplex (HD)/full-duplex (FD) wireless distributed relay systems. The main objective of this paper is to determine a set of relay amplifying matrices and transmitter/receiver beamforming vectors under transmit power constraints at the source and the relays, individually and independently, based on the minimum mean square error (MMSE) criterion. Additionally, the achievable rate and the MMSE cost function (CF) behaviors will be investigated numerically and analytically for both FD and HD distributed relaying systems. Finally, an iterative algorithm is proposed to solve the desired optimization problem.