Hi. My old Laptop hard drive has given up the ghost. The hard drive was a Hitachi with an interface IDE/ATA-3. Can I replace it with a Hard Drive with an interface of ATA-4. Thanks.

Basically yes.

The ATA-4 (which has a higher data transfer rate) may only run at the ATA-3 speed depending on the motherboard support.

ATA-3 / EIDE

ATA-3 is a standard approved by ANSI in 1997 under document number X3.298-1997. ATA-3 added additional security features and the new S.M.A.R.T feature.

ATA-4 / ATAPI-4 / ATA/ATAPI-4

ATA-4 is a standard approved by ANSI in 1998 under document NCITS 317-1998. ATA-4 includes the ATAPI packet command feature, introduces UDMA/33, also known as ultra-DMA/33 or ultra-ATA/33, which is capable of supporting data transfer rates of up to 33MBps.

http://www.computerhope.com/help/ide.htm

The most important question is the physical connector. Some laptops have specific cradles or connection adapters but at some point they should all be adaptable. Of course assuming the same size:

Laptop hard drives are compact drives that have a 2.5" form factor, as opposed to the 3.5" form factor of a standard desktop PC hard drive.