Won't even start up

When I start my computer (the other one) a couple of lines of DOS appear, then the screen goes snowy and stays like it. Vista doesn't even get the chance to do its stuff.

What is new or different since the last time everything worked properly (ie, new hw, new sw, virus, error, etc)?

Nothing at all. I can't be sure there's not something like a virus, of course, that I wouldn't know about, but the problem seems completely spontaneous.

Do you hear any beeps at boot?

Can you get to the advanced boot options screen (as soon as the system starts to boot begin tapping the F8 Function key)?

And last, do you have your original Vista cd?

There's one short beep immediately after switching on:
Holding down f8 while starting makes no difference:
And nor does starting with the Vista reinstallation DVD in place.

Go into the bios and move the cd drive to the first device in the boot order. Save the change, put the Vista cd in the drive, and reboot. Then run the Vista Startup Repair Options and let's see what happens.

No, I can't go into bios: within a few seconds of switching on there's just a snowstorm on the screen and nothing will shift it.

Have you tried a different display? Let's make sure it isn't something as simple as that (please also check all connections to and from the display).

I've checked all the connections, and it won't be the monitor as the few words of DOS that appear don't change, although they're different words each time, sometimes the manufacturing date, sometimes just a blinking underline, sometimes the Dell logo throught the snow. Sometimes it's the entire screen under the blizzard, other times the blinking underline just shoots down the left hand side of it.

I'd still like to try a different display. But if you don't want to do that you can try the standard stuff:

1) Download the diagnostic utility from your hd manufacturer's website, burn it to disc and run it

2) Download memtest (http://www.memtest.org/). Burn it to a cd, make sure the cd drive is at the top of the boot order in bios, then boot to the newly created cd and run the utility.

3) Take the cover off the computer, carefully blow out any dust, check to see all cards are firmly seated and all connections are tight.