Possibly, but it will be differcult, if its a Duron CPU it might be socket A and if so you MIGHT be able to put in a faster Sempron processor, if its the socket before socket A you might as well forget it. Download SIW or Belarc or Everest and give us the make and model of the motherboard, we should then be able to tell you if its possible or not click hereclick hereclick here It all depends on what socket the CPU is and whether the board can support a faster chip.
Board click here check visually its the same and CPUs and from this it can take up to an XP 2000 socket A processor click here but you might need to update the BIOS. I could find no mention of Semprons so perhaps this is as far as you can go, unless someone else can help here. You could email Matsonic and see if they answer. Failing that the only way you can get a socket A 2000 XP chip is second hand off the likes of Ebay. They are cheap but I wonder if its worth it.
I've just had a rummage. I have here a Duron 1400, is yours a 750? If it is and you want to try the 1400 email me via the envelope next to my username and I'll send it to you. I know it works, you'll just have to buy some thermal paste to change over chips. Let me know if you want it.