I feel having extra power is nice to have and should post no threat to your motherboard. Just make sure it has all the same connections you are using now.
What have you added to the Presario recently? That's a big difference in power you plan on upgrading. Chances are it will run fine using the 250 watt PSU because Compaq chose to use it (stock). Unless you added extra RAM or changed out the video card to a better grade, or even a second hard drive, a higher rated PSU would be much better, perhaps a 350-400 watt (also extra safety margin is included).
