Vista problem - unable to shut-down/log-off, or open task manager or install ANYTHING

Hi all

My dad just got a brand new Dell desktop comp, it's Windows Home Premium and was working fine for a few weeks before disaster struck. I have no idea how or why, but i'm beginning to suspect a virus, but not sure either way.

Symptoms are as follows; when shutting down, it simply doesn't, just sits on the spinning window's logo, and HDD still making noise, and never changes. I've done some research and this is a common enough problem. However, here, it's linked with another slightly less common problem, which is, task manager will not open, tried CTRL ALT ESC was well as CTRL ALT DEL, and it still opens in the tray.

Lastly, which led me to suspect a virus, is when we try to install a virus scanner, or even run on from the net, nothing happens. Downloads and extracts fine, but never begins to install. Even the windows restore programm thingy won't install.

I've tried everything i can think of, which honestly it's much considering i can't open task manager, or install anything.

So a brand new computer, is stilling gathering dust, my old, is furious and has rung Dell, who are completely unhelpful (and this is the 4th comp we've bought from them!).

Only other thing i can add, is we had Norton install at the time of the original issue, which we first suspected, so we removed, forcefully. And now we can't install anything else on it.

Thanks in advance,

Hawk