Do you have to buy Cannon accessories for your Cannon digital camera?

Or can you buy a generic brand and have everything work the same without causing the camera to blow up or stop working?

I'd like to buy an off brand battery charger (DPS-5000) and memory card (Sandisk 1GB). Dell offers both of them, and I get a 15% discount from Dell on all my purchases.

You can use other brands such as SanDisk for memory cards, or generic brand batteries.