Horizon not opening/working Windows Vista

Hey when I installed Horizon and tried to open it up it came up with this:

‘Error parsing
C:\Windows\Microsoft.NET\Framework\v2.0.50727\config\machine.config
Parser returned error 0xC00CE556’

Could some please help me out!?

Reinstall .net framework 3.5

This is not an error with Horizon but an issue with your computer. I suggest you try googling answers until you find one that works.