Top Portable software?
To work with MP3's you need to download an extra file ...here are the instructions. IT's just not included with Audacity because of licencing...
Adding LAME MP3 and FFMPEG Support
To add LAME MP3 support to Audacity, download Lame and unzip the download (get the ZIP download, the second link in the center). Place lame_enc.dll in your AudacityPortable\App\LAME directory. Audacity Portable will automatically detect it and set Audacity to use it on launch.
To add FFMPEG support to Audacity, download the alternate zip for Windows package from the Audacity website and unzip it. Extract all files to AudacityPortable\App\FFMPEG. After starting Audacity Portable, go to Edit - Preferences. Select Libraries. Click Locate under FFmpeg Import/Export Library. A box will appear saying that the library has been automatically located and asking if you still want to locate it manually. Select No. Click OK in Audacity preferences.
Gimp - the quality painting program
Just discovered, but not tried (thanks to ICT Magic)
OOo4kids - A kid friendly Open Office
Just tried it. it's basic, but it works.