Wal-Mart is whacking prices on PCs and TVs in a bid to expand its electronics business. The retailing giant has started selling a Compaq laptop for $398 a few weeks ahead of Black Friday, the day after Thanksgiving and one of the biggest shopping days of the year. Wal-Mart is also touting a 42-inch Panasonic plasma TV for $1,294 (down from $1,794) and a 37-inch HDTV LCD from Panasonic for $997 (down from $1,297).