We present new spectroscopic and photometric observations of the cool DAZ white dwarf G74-7. These data are combined with archival HST Faint Object Spectrograph data covering the range 1700-3200 Å, allowing estimates of the Ca, Mg, and Fe abundances in this object. Our analysis suggests that G74-7 is a hydrogen-rich star of normal gravity, with Teff = 7320 K and the following photospheric abundances: log (Ca/H) = -8.8 +/- 0.2, log (Mg/H) = -8.1 +/- 0.3, and an upper limit to log (Fe/H) <~ -5. These new results are considered within the framework of current models proposed to explain the presence of heavy elements in the high-gravity photospheres of white dwarf stars.Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract No. NAS 5-26555.