I assume that you have Power DVD version 4 or 5.
How much RAM do you have?
My personal minimum for XP is 256MB. With on-board video, you need at least another 64MB of RAM, or 320MB for things to operate anywhere near smooth.
In BIOS settings, how much RAM is set aside for the video system?
It needs to be at least 32MB.
While you technically may meet the minimum system requirements for Power DVD, I suspect that the real root of your problem is the on-board video.
"Typically", on-board video has 10 percent of the performance of a plug-in video card. Some of this comes from the shared resources and thus slower RAM access speeds.
A lot comes from the fact that most motherboards with on-board video and sound are "price-point" items. The parts are chosen to meet a selling price target, not a level of performance.
IMHO, systems with on-board video are best left to simple tasks such as basic word processing and web browsing. They simply are not up to the task when called upon to run involved graphics applications.
You can try adding RAM, and dedicating more RAM to the video system, but your best option is to get a good PCI video card.
Chas