Portable apps won't have a lot of artifacts, but there is a list in the registry of the execution I don't recall the path off the top of my head and the structure can be a little difficult to dissect but you can look at some of Eric Zimmermans tools.
You can grab the prefetch cache for a quick idea of what has been executed lately.
"Installed" applications will usually be stored in subkeys located under one of two registry keys
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall
32 bit applications on a 64-bit machine
HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall