You made your file in notepad, you said so yourself:
I've made the file using notepad...
So yes, you can load .sqs files in notepad. They are just text after all.
Anyway, could you describe the error message a bit more?
Like: Where do you get it?
When saving as .sqs, when loading the file in OFP, when renaming to .sqs?
This is how you create new .sqs files:
Open up notepad (or texteditor of your choice) and write your script.
Then select "Save As".
In the Save As dialog, select file type: All Files *.*
then write
YourScriptName.sqs in the file field.
This is how you make a .txt into a .sqs
First off, in Explorer. Go to Tools - > Folder Options - > View
And find the place where it says:
Hide extensions for known filetypes.
Then you find your file,
YourScriptName.txt, right click and select "Rename".
Remove the .txt part and add .sqs.
Some times your file is saved as
YourScriptName.sqs.txt in which case you just follow the above instructions and remove the .txt part.
Now, that will get you a working .sqs file. I can't troubleshoot the script itself, since I haven't seen it, but this will produce a .sqs file readable by OFP.
Cheers, KTottE
PS. Oh, and I moved this to Scripting: General since it had nothing to do with Cutscenes ;D