You need an Admin account and password. The Privilege Set(s) you're currently using don't allow record deletion. As far as I know there's no bypass and FMI no longer recovers lost passwords. Someone else may know more . . .
Have you tried performing a recover on the file? It may be that your file is damaged. Given the age of this version and the fact that you can't get any help from the original developer severely limits your options here.
You may have no option but to export the data int a text file (if you can even do that) and import it into a brand new database designed by you or some one else.
I have tried recover menu item. And it say successful, but still have the same error:
"There was a find error. This may be caused by a locked record. Please verify that no other users are accessing this record and try again. (Find Sale)"
And of course, it's running only on one computer. Although the developer does not support it any more, he does have on his website FAQ of this problem describing it being caused by voided transaction at the time of PC crash or some sort causing file lock. And it suggests going in and deleting that voided record to resolve the issue. But no way to delete that record.