Is Maxima available as a "portable" app for Windows ?
"Portable" apps don't mess with the Registry, and they require only a limited number of read-only and read-write file locations.
This allows the apps to live on a flash memory USB drive and be executed on a PC _without having to install the app on the PC itself_.
In normal practise, the app is "installed" on the USB drive, and then merely inserted into the PC. The PC can then merely execute the app directly from the USB drive; all of the usual information that the app needs is on the USB drive, and any databases it needs are also on the USB drive.
A Portable Maxima could be carried around on a USB drive, along with all of your own Maxima programs and data, which would allow you to run Maxima on nearly any PC that you have access to -- without having to "install" Maxima on that PC. Thus, if someone has a high performance PC & your home PC is too wimpy, you can plug your Maxima into the more powerful PC for a particularly difficult computation.
More information here:
http://portableapps.com/http://portableapps.com/development