What's the best Anti-virus for my new computer?

[Mardor]

My sons have an HP one year old laptop running Vista Home Premium 32 bit. Of course, just turned a year old two days ago and warranty is now up. There is not a lot of software on this thing. I installed ESET Nod32 and it runs well. I just scanned and there are no threats found. No popups are appearing in IE. There is no sign of a virus anywhere. There are multiple problems that I cannot figure out. When we try to shut the computer down, it gets stuck in Logging Off screen. I try Ctrl Alt Delete to bring up Task Manager but it will not appear. I get the Icon down in the lower right part of the screen, but cannot click on it to open it up. I tried to do a System Restore. I select it, but nothing happens. When I try doing it all over again, it says that it is already running, but it is not. I have tried uninstalling things they dont need but the uninstall freezes up also and when i hit cancel, it just remains cancelling without doing anything. I am usually pretty good at fixing things but this one has me stumped. If I could just do a restore, i feel like i could get it back to where it was before this started happening a couple of days ago,. Any help is appreciated. hydroxycut reviews