Go to outlook express>tools>options>maintenance>store folder and note this location. All your files are stored here as dbx files. These could be copied and later can be extracted using suitable programs, google for 'extracting from dbx'. Alternatively you could copy them onto a folder on your new computer but it all gets messy.
Clean the computer - take out the hard drive and after drilling holes in it, submerging it in a bucket of water hit it with a large hammer