Complex sentence: GBA video paks were the feature prize in Vol.183 of "Nintendo Power" Magazine, as part of its players poll sweepstakes, in which five grand prize winners would receive a GBA SP and twenty GBA video paks.
Split into simpler sentences: GBA video paks were the feature prize in Vol.183 of "Nintendo Power" Magazine, as part of its players poll sweepstakes. In which five grand prize winners would get a GBA SP and twenty GBA video paks.