My desktop PC ( new at xmas) uses DDR memory, somebody told me that not all DDR memory is the same, is that true as I need to add some memory to speed things up.
There are many types; DDR PC2700, 3200, 3500, 4000, and 4400. The most common at the moment is DDR PC3200.
Motherboard manuals will generally specify the maximum type they can support, since a a motherboard that supports DDR PC3500 will support anything below that.