Download EasyWinBuilder together with Bitcoin v0.8.3:
https://github.com/phelixbtc/bitcoin/archive/0.8.3-EasyWinBuilder-v0.2.zip
(all code is equal to v0.8.3, only the easywinbuilder folder is new - compare to Bitcoin v0.8.3, not to master)

Simply double click __all_easywinbuilder.bat in the easywinbuilder folder and follow instructions.

Readme:
https://github.com/phelixbtc/bitcoin/blob/0.8.3-EasyWinBuilder-v0.2/easywinbuilder/README.md

There is an almost identical Namecoin version here: https://github.com/phelixnmc/namecoin-qt

It should also work with altcoins with a similar structure to Bitcoin, simply copy&paste the easywinbuilder folder and edit the coinname variable in set_vars.bat.

Based on the build manual by nitrogenetics (https://bitcointalk.org/index.php?topic=149479.0) and older manuals from others.