Workgroup to Domain back to Workgroup

I have a NT 4.0 sp3 workstation that I had set up for workgroups. Somehow, someone got access to the administrator password and changed to be part of a domain. Now, I cannot switch it back to the workgroup. It seems my only option is to reinstallNT 4.0. This particular station has our accountant’s quickbooks installed on it. If I reinstall NT, will it delete all of her quickbook programs and necessary files?