My budget is around 700-900 bucks, and i want a m/b that has built-in vga and sound. does anyone have any problems with sempron?

I relize you're on a budget, but are you intending to play any games ?!?

If so, then ditch the idea of using the onboard graphics card and go with a lower-end graphics card like the nVidia 5200 or the ATi 9200 series cards. Decent graphics and gameplay for not much money

As for the Sempron CPU, it's basically a rebadged Palimino core Athlon XP. It's actually a decent CPU for the price. The sweet spot seems to be the Sempron 2800+.

Or go with the Sempron 3100+, where you can easily upgrade your processor to the more robust amd64s (Sempron 3100+ is socket 754).