Cannot create file "C:\windows\system32\drivers\etc\hosts" access denied

[warriorautotech]

My computer was recently infected with "personal internet security 2011" virus, constant popups I could not access security programs,no restore points. I ran something called rkill and scanned three times with malwarebytes. I also ran a registry repair program, dont remember which one.Computer is running better but still having problems, forward and back buttons dont work properly , search results sometimes jump websites, google preferences says cookies disabled, right click doesnt work properly, other problems.
I recently scanned with spybot in safe mode and got some results i couldnt fix
Fraud.WindowsProtectionSuite
Microsoft.Windows.RedirectedHosts, several entries on both
the message i get when I try to fix these problems is Cannot create file "C:\windows\system32\drivers\etc\hosts" access denied
Can anyone please help me with this? I really dont want to reload my operating system.( Windows Vista Home Edition) Thanks in advance.
My computer knowledge is very limited so please be understanding.

[tashi]

Hello warriorautotech,

Please see this forum's sticky which also includes instructions for posting a preliminary DDS log in post #2. "BEFORE you POST"(READ this Procedure BEFORE Requesting Assistance) (http://forums.spybot.info/showthread.php?t=288)

Then start a new topic and a volunteer analyst will advise you when available. :)

Best regards.