My understanding of PortableApps, is to have access to your personal tools and files without leaving traces of them on the machine being used (confidential reasons).
I would like to point out that I have noticed traces of Thunderbird on WinXP under %username% settings.
I haven't completed a full analysis to determine if other Apps leave traces and if this is due to settings in the Apps. Nor have I yet to provide possible locations of these traces and to what extent they can be manipulated.
Some tuning may be required on the Application or PortableApps.
Thank you.
We'd need more information than just "somewhere under the USER directory" to determine what you're referring to. There should be no personal information left behind and nothing other than the usual Prefetch stuff stored as well as possible registry trace of recently run EXEs depending on how the system is configured. Both of these are in locations you can't clear unless you are logged in as an admin.
It is important to realize that every app you use on any system will leave traces in prefetch and other locations as well as be visible to network analyzers. Anyone who tells you otherwise is either lying to try and sell you something or doesn't understand portable software and Windows.
Sometimes, the impossible can become possible, if you're awesome!