I looked up your laptop model, and it has an Intel built-in graphics card soldered to the motherboard. This card uses system RAM and I'd suspect this as one potential source of your program, since it means the graphics card is competing with your PC's processor for RAM access. The other potential source is the software - Windows Media Player. Try using VLC instead for non-DVD videos, and the following for DVDs:
PowerDVD WinDVD
Both can be downloaded for trial, and if one works without skipping you can purchase a license.
If a software solution doesn't help, you unfortunately can't upgrade the graphics card since it's soldered on, but you can install more RAM. You might try upgrading to 2Gb of RAM to see if it helps (it certainly can't hurt, and RAM's pretty cheap these days).
Vasily