Portable Notepad App

I would like to create a basic notepad application which saves the contents to a text file.

Would it be possible to make an application like this which can run from a USB and on any pc with the .NET framework installed ?

If so, how would I go about this ?

Also, which .NET framework should I build it with to ensure it will run on the majority of PC's as some are not up to date ?

Thanks,

Michael