>3 How do i install applications I have downloaded , for instance, gpe-clock-0.25.tar.gz when i double click on it the message comes up 'unknown file type'

If you choose to download and install (as opposed to directly selecting installable apps from the application manager), then don't download .tar.gz files - that's most likely sourcefiles or some such, and not what you want. Look for the .deb files. (or rather, *.armel.deb). These can be installed by the application manager, or, if downloaded with the opera browser it'll recognize those as well (possibly even the file manager will).