Modern traditions and honest for Windows software say any program wanting claim itself "serious" and "professional" must have an installer. Despite of how large a program is, how many resource files, libraries and components it uses, and how deep its system dependencies are, user wants to just download a single "SetupMyProgram.exe" file, run it and have it ready to go.
Preparing an installer is not-so-easy task. Yes, there are simple cases where packing all files with a small "runner" is enough. But even in such case your "simplest possible" installer must perform a bunch of non-trivial tasks, like checking for previously installed versions, updating shortcuts, and so on.
The not so simple (as for capabilities) but still simple (as for usage) setup builder solution is Smart Install Maker. Besides the "standard minimum" - slick modern interface, displaying licenses, creating shortcuts and Start menu groups - installers, created with this software, can do all up-to-date advanced tricks. Checking whether .Net framework is installed, checking its versions, registering ActiveX-es and system libraries, flexible INI and Registry keys from files, and even collecting uninstall feedbacks on the vendor's Web site.
Coupled with good compression algorithms and small size of the installer, this program's runtime capabilities result is in the best-for-everyone installers; and well thought-out highly usable interface of Smart Install Maker does its better to the installer creation speed and pleasure.
"I downloaded the trial version and was impressed, so much so that after doing a few tests, I bought it. The project I need it for is 240 Mb is size and contains more than 10,000 files. A previous installer took over an hour to install all of these files. Your product did it in less than three minutes."