There are 2 sensors at Inspiron1501. They are Winbond (formerly Nat'l Semiconductors) PC87591 SuperIO chip and AMD K8 CPU embedded sensor.
Winbond PC87591 is not supported, and obviously will not be. Well, no hard feelings, as it seems to control laptop fan perfectly.
AMD K8 sensor is supported, seek for k8temp module.
[will be continued]
to-do: temperature sensor software overview.