The Kingston models you show are indeed SDRAM DIMMS. The PC100 and PC133 refer to the bus speed of the memory. Your Duron runs on a FSB speed of 100, so putting in 133 memory will not offer any performance advantages as it will be limited to running at 100.
The latency is how many clock cycles it takes to fetch data from the memory. The lower, the better. Your current memory has a latency of 3. The recommended ones have a latency of 2.
If you are looking to upgrade, I'd suggest getting out of the Duron series of chips and into the Athlons. You will receive a large performance increase (due to more cache as well as higher clock speeds). You can easily upgrade your entire system with a new motherboard, memory and cpu for under 250 dollars. If that is a stretch, your best bet is to get rid of the Duron and go with the Athlon. A 1.4 Gig Thunderbird can be had for about 50 bucks.
