Can a SD (memory card) be used instead of XD card in a digital Camera?

Typically a digital camera is designed to accept 1 and only 1 type of storage card. so, no.

NOT A CHANCE.

What does your camera say. I use SD cards in my digital cameras.

Not unless your camera has dual card slots. Having said that, I've only come across SD+CF, XD+CF or MS+CF combinations so far. If you only have an XD slot it won't work. The phiysical size of the cards differ too.