word doc opens then begins to shrink until it gets to 10%

In Word 2003, I open a doc and it begins to shrink until it gets to 10%. I tried changing the view but it didn’t make any difference. I changed the viewing percentage to 400 and the doc changed but began to shrink. If I click and hold on the page before it gets too small I can look at the doc. But when I let go of the nouse, it shrinks down again.
Also, when I type an email address in outlook express, the font starts to grow until I can only see the bottom bits of the text.
Both of these things started at the same time so I was thinking a virus. I haven’t found anything on the web. I ran a virus check and it found nothing. I also ran adaware and spybot and I am still having the problem.