I think that the details I gave earlier this year related to Quicktime, but the principal is the same. In this case, open RealPlayer and take this path:

File - Preferences - Upgrade - Media Types - Re-Associate

Uncheck the boxes in the "Re-Associate" menu for any file-types you want RealPlayer to keep its paws off. I have version 8, too, but I seem to have avoided installing RealDownload Express, fortunately. Disabling "Browser Watch" may very well solve your problem; I've disabled most of RealPlayer's automatic features, as they are mostly a bloody nuisance!