INT 2F - TBSCANX - INSTALLATION CHECK
        AX = CA00h
        BX = 5442h ('TB')
Return: AL = 00h not installed
           = FFh installed
                BX = 7462h ('tb') if BX was 5442h on entry
Program: TBSCANX is a resident virus scanning module by Frans Veldman.
Note:   programs may perform virus checks on themselves, other program files,
          or their data files by invoking the TBSCANX API.
SeeAlso: AX=4653h,AX=C900h

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