My OS is XP Pro SP3 and I use Word XP. When I select a line in a document to use bold/italic/underline or to justify the margin the whole document changes. This is a new phenomenon which I have been unable to remedy. I have uninstalled Word 2007, in case it was the cause of the problem, and uninstalled and reinstalled Word but to no avail.

I'm tearing my hair out. Help please!