Semprons are for 166/333MHz FSB, do not bother with them for that motherboard.
Anyway, see if you can figure out which of these two motherboards you have:http://www.magic-pro.com/product/socket462/7vipax2.htm
The second one should support Athlon XPs, whereas the first one probably doesn't. If you've got the second motherboard, then an Athlon XP 2400+ would probably be the best CPU for it. A 1.3GHz Duron or 1GHz+ Athlon Thunderbird for the first.
I wonder if this Magic-Pro is an alias for PCChips. Their website is full of flash animations and uncompressed images.