I'm also having this problem with hijackthis. Everytime I try to run I get (see attachment ERROR), and when I do what I try to do what it says it doesn't work either. I've also attached the host file. When I right click on it and chose run as administrator it works fine, but I am logged in with the admin account so i shouldn't have to say run as administrator. I never had this problem before when I uninstall and reinstall the application after a bit the same thing starts to happen again but when I go to http://www.hijackthis.de it shows everything on the computer is safe but i know there are still problems becuase my IE keeps crashing.
So I downloaded and installed some programs Uniblue RegistryBooster 2, Uniblue SpeedUpMyPC, Ad-Aware SE Personal, Kaspersky Antivirus and ATF-Cleaner, which I only used the free trials. The new PC I bought came with Windows Defender preinstalled already. I have since uninstalled Ad-Aware , Uniblue RegistryBooster 2 Uniblue SpeedUpMyPC, and Kaspersky Antivirus. All the programs came up saying they found threats and I was able to remove what came up, after manually doing most as I was limited removing some stuff with the programs I had downloaded, but I am still not convinced my issue is resolved as my computer is very slow.
I have attached my latest scan (#3)