Major XHTML conversion

Hi guys,

I'm about to embark on a major XHTML clean up of one of our clients 
sites, they have migrated to a new CMS, and all the HTML was brought 
over as is, and it needs to be converted into valid XHTML strict.

Since the site has around 20,000 pieces of content, I don't really want 
to have to do this by hand, so I thought tidy would be the best 
solution, it's easy enough to use on a localised site, but I'm not sure 
how I would go about plugging it into a database?

Any help, suggestions or tips would be much appreciated

Thanks in advance

Colm