error message on installing a demo

Error message when installing a demo program on a Fujitsu-Siemens Amilo laptop, 3.06GHz, 1GB, 80GB, ‘c:\windows\system32\autoexec.nt. The system file is not suitable for running MSDOS and Microsoft Windows applications. Choose close to terminate the application.’ There is no such file, even hidden. The author of the software Scriptware for Windows cannot help, nor can Fujitsu-Siemens. It does not affect other software installation. Formatting is not an option, can anyone help please?