Dez Hardwarez was seemingly a supplier of hardware and other similar products based on Bountiful in the central compound of Helaman Township. As the name suggests, it was owned by Dez.
Whether the store actually existed cannot be said with certainty, as it is only seen in the memories of neural resocialized Marine Ardo Melnikov. In one set of tampered memories, the zerg invaded the planet, the store almost certainly being destroyed. Most likely however, the invasion never ocurred and the store still exists.
References
Hickman, Tracy. StarCraft: Speed of Darkness. Simon & Schuster/Pocket Books, May 21, 2002. ISBN 0-671-04150-9