  We present analysis of Chandra and XMM-Newton observations of three
early-type galaxies, NGC 57, NGC 7796 and IC 1531. All three are found in very
low density environments, and appear to have no neighbours of comparable size.
NGC 57 has a halo of kT~0.9 keV, solar metallicity gas, while NGC 7796 and IC
1531 both have ~0.55 keV, 0.5-0.6 Zsol haloes. IC 1531 has a relatively compact
halo, and we consider it likely that gas has been removed from the system by
the effects of AGN heating. For NGC 57 and NGC 7796 we estimate mass, entropy
and cooling time profiles and find that NGC 57 has a fairly massive dark halo
with a mass-to-light ratio of 44.7 (4.0,-8.5) Msol/Lsol (1 sigma uncertainties)
at 4.75 Re. This is very similar to the mass-to-light ratio found for NGC 4555
and confirms that isolated ellipticals can possess sizable dark matter haloes.
We find a significantly lower mass-to-light ratio for NGC 7796, 10.6
(+2.5,-2.3) Msol/Lsol at 5 Re, and discuss the possibility that NGC 7796 hosts
a galactic wind, causing us to underestimate its mass.
