Asus isn't the only one with bad support, this happens everywhere...
When you have an issue, it's always best to consider if it's something you can do on your end without Tech Support, meaning, if you are into this stuff, then learn, and in time you won't ever bother calling Tech SUpport, and the only time you call is to submit a trouble ticket for bugs you've encountered to have them fix them.
1. Bad hard drive replaced
2. You should have a Windows Key
3. Download ISO Image, you didn't mention which version, so here's a link for Windows 7 if you have the key;
https://www.microsoft.com/en-us/software-download/windows74. Burn the ISO to either USB or DVD
5. Go to the Asus website and download the drivers for your laptop.
6. Install Windows and the drivers and you're done
NOW I highly suggest you learn about Clonezilla;
http://www.clonezilla.org/Clonezilla is VERY EASY to use, it has a 'Beginner' option, and it only takes like a few minutes to use, and this is what you want for making Backups of your system, so in the future something dies, you just reinstall your clonezilla backup image and you are up and flying again...