Am i correct in thinking that if you look at emails via the preview screen you should not be hit by a virus. that only when you actually open the email can the virus gain entry? Is this an old wives tale?
Very rare you will get a virus by looking at an email. You usually have to click on the link or download the "greeting card from a friend" before the nasties strike.
"Am i correct "
No. The only difference when viewing in the preview pane is that the message is opened automatically as opposed to manually. In either case it's opened, and in the rare cases where opening it would result in infection, then previewing it will have the same result.
This is why most people advise turning off the preview pane altogether - because it won't even let you delete a suspicious e-mail without first opening it (i.e. as soon as you click to select it for deletion, it opens in the preview pane).
One more thing. Often email worms function through a hole in Outlook's code (or many of the older ones used to, anyway).
Using a different mail reader, like Thunderbird, will result (for now) in greater chances of being safe, simple because fewer worms are written to target this client.
Even better is using a web-based service like Gmail, through your web browser.