Can a SDHC memory card be used in a sony dcr-sr42 camcorder?

No, the Sony DCR-SR42 camcorder does not support SDHC memory cards, as it is designed to use a built-in hard disk drive for storage. It primarily records video onto its internal HDD and is not compatible with SDHC or SD cards. For external storage, you would need to use the appropriate formats supported by the camcorder.