The Edgar filing online: http://google.brand.edgar-online.com/EFX_dll/EDGARpro.dll?FetchFilingHtmlSection1?SectionID=48894-3765-6545&SessionID=Gp_vFHC7QJT3N57 reflects that in the late 90's, Merrill Lynch Group Employee Services handled the plan. You may want to try to reach out to them to see if they can help you: http://www.ml.com/index.asp?id=7695_114042 is the link to their contact information. Best of luck to you. You may get the runaround until you get to the right department.
Oh boy...looks like CompUSA has changed hands numerous times since then. See here for the timeline: http://en.wikipedia.org/wiki/CompUSA You might try calling their current owner, Systemax, to see if the account is in their 401k plan, or if they might have any further information. The headquarters is 516-608-7000, and you'll likely be transferred a number of times. Explain the situation and say you need to speak with someone in benefits. You may also have difficulty if a beneficiary was not designated.