...or downloaded videos? Have you checked the computer for viruses and spyware using a variety of removal tools? If so, which ones?
If they're online videos, what type of connection do you have? A dial-up connection will frequently do that..There's really no way to solve the issue unless you get a faster connection.
If the files are downloaded videos that are on your computer's hard drive, then you may have too much stuff running in the background hogging up resources..Try the steps below:
How To Shut Down Unnecessary Start Up Programs
How To Clean Unwanted Files From The Hard Drive
After all of the above, including running Scandisk and Defrag, restart the computer..When you're ready to play the videos, temporarily disable your antivirus programs to free up the resources as well.
Hope this helps.
Im using my HP desktop for school projects and playing videos/music. It still runs win 98 and has pentium 600 mhz w/ 384 mb ram. my mpegs and avi files always lag behind like the image is way behind the audio. I tried all the media players like divx,wmp,realplayer,and winamp but each one falls behind. is there a really good media player out there or how can i improve my performance to eliminate lag?