That's difficult.
I just counted on my Windows 7 PC.
I have some 2250 .exe-files on my PC (admittedly, some 65% in c:\windows\winsxs, c:\windows\installer and the recycle bin) and some 100 .com-files. You might not be interested in all those files.
Then of course we have the control panel applets, the jar-files (java executables), the services, the screensavers, the vbscripts, all of which can easily be described as programs also.
So listing just the things you're interested in on one PC is an interesting task also. Once it works in one, it's relatively easy to run it in all from your USB-stick.
One interesting detail: different drives. Here at home, my p:-drive is a local drive. Programs there should be included in the listing. At work my p:-drive is a network drive. That doesn't count as "on that PC". And if I happened to have a USB-stick or a CD in the drive which had .exe-files, would those count as being "on that PC"?
Kees