I'm not an Android user, but as far as I can tell, the HTC Desire 500 runs the 4.3 and Sense 5.MR operating systems.
Kit Kat, which is the 4.4 update of the Android operating system isn't available for HTC Desire 500.
You might also want to check out the Android Kit Kat website, I'm pretty sure it has a list of devices that are Kit Kat enabled here: http://www.android.com/intl/en_uk/phones-and-tablets/
