Maybe I am misinterpreting your issue, but...
Is this a file created by the QBasic program?
If so, consider that QBasic normally can only handle files via the old DOS 8.3 naming convention, which does not support lowercase letters. No matter what you use in QBasic the final filename will still be 8.3 uppercase format. If you create such a file with QBasic you may need to rename the file with lowercase letters before transferring it or transfer the file as a lowercase-named file.
For example, in FTP from the (I assume) Windows machine use:
[tt]put FILE.TXT file.txt[/tt]
If using a "GUI FTP" client you will have to do something similar there as instead. You may have to turn on an option to be prompted for the "as" name.
Under Win 9x I recall that renaming a file from an uppercase name to the same name in lowercase sometimes did not seem to work. In such a case rename the original (uppercase) filename to an intermediate name, then to the final desired (lowercase) name:
[tt]ren FILE.TXT x.txt
ren x.txt file.txt[/tt]
The same thing works when renaming from within Windows Explorer (via right-click, Rename).