Shares in Egghead.com Inc jumped as much as 19% Tuesday after the internet retailer announced that it had signed a deal with Microsoft Corp to sell software on the MSN Shopping web site. The deal will see Egghead become the premier software merchant on the site and will also receive advertising support on several other MSN sites. No financial details were disclosed. Egghead says its online software store offers thousands of titles, including about 4,000 that can be downloaded. It has already signed similar agreements with Yahoo, GeoCities, @Home Network, AOL, and Netscape, among others. Egghead stock closed the day up $1.5625, or 9%, at $18.875.