This is how I solved that problem:
1. Check your folder there C:\Program Files (x86)\SquareEnix\FINAL FANTASY XIV - A Realm Reborn (for Windows 7), and right click on it.
2. Click on Property, General, and uncheck the "Read only" line at the bottom of the window.
3 Press OK, and then open your folder "boot".
4. Right click on ffxivlauncher.exe, Properties, Compatibility
5. Activate Windows XP compatiblity mode

My DL and installs immediatly ran flawlessly once I did this, I hope that'll help.
Also, be sure to run as Administrator, still by right-clicking the ffxivlauncher, "Run as administrator".

Good luck!