An all-in-one instrumentation system design for immunochromatographic assay with Windows XP Embedded (XPE) Approach is presented in this paper. The proposed system can determine the concentration of target analyte within a few seconds, which can be used in a wide range of applications. This paper also presents a new image analysis algorithm to perform the unsupervised classification for the immunochromatographic assay with high-definition webcam. The overall development scheme is explained with real examples. The Windows XP Embedded approach makes it easier to get our system with up-todate peripherals to market. That is crucial for short life-cycle peripherals on market. The overall development scheme can be applied to other Windows XP Embedded compatible system design as well. The platform EPIA-P720 is employed as a demonstrating example. The overall system functions are verified by experimental results.