It is an anoying little bugger isn't it. It is an updated version of the XP version. It made changes to your registry so to every exe file you open gets opened via Antivirus Vista 2010. Irritating because the same stuff happens in safe mode.
Some programs works when you use "Run as Administrator". To get rid of it try to install malwarebyte.
Run your computer in safe mode with networking. You might use google chrome for browsing. To start your browser: select start menu end then rightclick on your browser icon and select "run as administrator". download malwarebyte and save the install to your desktop. Right Click the malwarebytes icon and select "Run as Administrator".
The program will install. From the startmenu richtclick on the malware icon and select "run as Administrator". Maybe it will update first. If that happens, wait untill the update has finished and then run it again as administrator from the startmenu. MalwareBytes should start. Run a quickscan. It will find a trojan and a rootkit (tdds) and some other stuff. Remove it.
Than run explorer as administrator and also run taskmanager as administrator. If taskmanager is running you will still see a process called av.exe. Stop this process and delete the av.exe file from your user folder C:\Users\%userfolder%\AppData\Local
If you cannot delete it at once, rename it first.
If it is deleted you still have the faulty shell open commands in your registry. You can do this by selecting exe on this page if you run vista http://www.winhelponline.com/articles/105/...dows-Vista.html
download the reg and install it.
The file associations are fixed now. You can check by normally clicking on a program icon. The program should open normally.
after that open regeditor and do a search on "av.exe". Delete these keys.
Hope you will manage