I've tried other methods, but these two ones were the easyest to do.
Method 1:
https://bitcointalk.org/index.php?topic=252931.0;topicseen
Really easy: download the package on a clean pc (i've used a virtual windows XP in the past, worked like a charm), run it => finished
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If something goes wrong, open the .sh files, and execute the steps it lists one by one.
This method is the easyest... it requires almost no knowledge, but if something goes wrong, it can be pretty hard to figure it out.
Method 2:
https://github.com/bitcoin/bitcoin/blob/master/doc/gitian-building.md
I know it sounds scary to build a windows exectable on linux, but it's the easyest way
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BTW: you don't need to do anything to your windows pc, you just run linux in oracle virtual machine under windows.
If you've tried both methods, but cannot succeed, post the error messages in this thread and i'll have a look.
Good luck!