Okay, I've tried installing Lightroom 5 on my pc and after installation and before I type in the serial number, I get this "assertion failed" message, and windows shuts the program down.
You may refer to
"Assertion failed" update error | Windows
Make sure you have Read write access to "Pictures"folder" in C:
Also try to trash Lightroom Preferences by holding down CTRL+ALT+SHIFT while starting Lighroom,select yes on the Prompt to reset Preferences
Hope that helps
Retrieving data ...