So much for Compaq Computer Corp’s plunge into the personal computer mass market: Alex Brown & Sons responded by downgrading its rating on the shares to a sell from a hold and the shares were off $1.125 at $26.25 in early trading yesterday; the analyst also cut his 1992 estimate to $1.45 a share from $1.82 and outlook for next year to $1.75 from his earlier $2.25 a share.
