You can make TestComplete save these files in ANSI. To do this, open the TestComplete project containing these files, open the project settings window (Tools | Current Project Properties) and set the ANSI value for the Units encoding option in the General section. After this, save the project (File | Save All).
Also, you can save the files in the ANSI encoding from Notepad. Just open a file in Notepad and save is using the Save As dialog (File | Save As). You can choose the desired encoding in the Enconding combo box in this dialog.