what is Error 0x8078002A

[Lea2015]

I have a 500gb external hard drive. It has worked well until know. My back ups keep failing giving me this error message 0x8078002A sometimes it says there is not enough space but there is plenty> any help is greatly appreciated

 

[SuperSoph_WD]

Welcome to the TH community, Lea2015!

This error is actually quite common for larger than 2 TB external HDDs. Basically, Windows backup and restore utility does not support 4K logical sector sizes, which are found on larger external drives. However, this is different from an Advanced Format drive (AFD) which use 4K physical sector sizes (with then, there shouldn't be any issues).
The solution to your issue is to re-format the external HDD back to its factory default format, however make sure you back up your data from the drive somewhere else beforehand (the re-format will erase everything stored on it). The factory default format should fix the sector size issue.
If interested, here's more info from MS knowledge base: https://support.microsoft.com/en-us/kb/2510009

Hope it helps. Let me know if you have more questions!
SuperSoph_WD