Event-related potentials (ERPs), specifically neuro-potentials, provide important clinical information about cognition and sensory-motor systems. P300 is a critical involuntary endogenous ERP elicited in response to a specific change in stimuli and can be used as a metric to assess attention. A noninvasive, cost-effective P300 extractor system was designed, developed, and validated for subjective attention and working memory assessment. Standard P300 three-event visual stimuli, consisting of randomly occurring small ball, big ball (response required), and checkerboard, were generated using code in the Presentation software. These stimuli were presented to subjects using a head-mounted display (HMD). Scalp-recorded P300 responses were acquired using an Open BCI Cyton biosensing board from young adults (n=5). To validate the extracted P300 response, the experiment was repeated on the same subjects using an FDA-approved CE-certified Neuroelectric Enobio 8 system. The extracted biopotential patterns from Cz and Pz electrodes, including peak latencies for P3a and P3b components, matched in both reference and developed systems. Furthermore, the ERP imaging shows inter-trial variabilities, and a gradual increment in peak latency confirms the fatigue phenomenon during the experiment.