Getlasterror: 5

Ok,

i am having this problem for sometime now and what is happening is i cant install itunes 11.1.5 for Windows (64-bit) the oringnal problem was i couldnt update nor uninstall so i used microsoft fixit thinking my problem would be over (i left Bonjour, Apple mobile support and itunes help but i deleted itunes and itunes update) but when i came to install itunes again BAM! same problem! What should i do, i need to update my apple tv and without any itunes i am kinda helpless.

PLEASE NEED URGENT HELP

Jason

PS i tried to follow Dreamyboys's advice and tried to install msicuu2.exe from MajorGeeks but when i ran it, it simply said access denied!