I have seen a couple of windows GUI front ends for AVRDUDE that allows simple selection of hex files and uploading.
Wouldn't that be part of what the OP needs? The other part would be rolling the GUI and hex files into a windows installer file, of which there are numerous examples.
Could be, the one I use still requires the user to know which comm port, which processor type, etc. I would think a true auto install windows arduino sketch loader would just emulate the serial protocol that the arduino bootloader uses (varies with chip type so that adds another problem). Here is what the one I use looks like: