All my music and videos on my computer skip. When

do a system restore back to before you had this problem.
click start then all programs then asessories then system tools then system restore.
click restore my computer to earlier date then click next. click the date before this occured then click next until your pc reboots. this will undo anything that you may have done to damage your system

Heres the issue: your bus thruput is being broken up into chunks. That may not make sense to you, but imagine a waiter in a restaurant. He is all alone, and the place is packed. Hes slowly serving everyone a little at a time, one meal to a table. Your pc is having that issue. PC's read audio and video files as data. The more bytes in the file (the size of the file) or the more complex the compression/decompression algorithm (codec), the more tasking it is on the cpu. There are a few things you can do to try to resolve this.
1. upgrade your ram. More ram in a computer means your computer can run more smoothly. Ram allows your machine to remember more stuff 'on the fly' without having to stop and write it down in a temp file (cache) for later use. Ram is always a great idea, no matter what.
2. Upgrade your video card. A video card with a high performance GPU (thats graphical processor unit) and a high amount of on-card ram (128 MB or higher is good) will render your images much more freely, (smoother, prettier pictures during movie playback) and allow your main processor to concentrate on the other aspects of your computer, rather than trying to render graphics or wait for your slower, weaker, on board gpu to render them.
3. save your documents to a flash disk and re-format your hard drive and reinstall windows and drivers. You said that it didnt skip before, so it is likely that your current ram and gpu are sufficient, but, that there is a 3rd party software piece working in the background, causing the stuttering. It might be harmless, or it might be malicious. It could also be your security software (some pc protection solutions are resource hogs). As a windows pc gets older, it gets slower because its registry (hive) is getting fatter, so it has to process thru a larger registry to do something. Reformatting destroys this large registry and resets it to the smallest it will ever be, until you reinstall things, like office or flash or java or yahoo or winamp or etc etc etc.
4. finally, it could be the renderer (program) that you are using to play the media with. I personally use Winamp for my music (mp3, wma) and I use "media player classic" (just search for k-lite codec full). media player classic is a bare bones audio video player, and comes with several up to date codecs for playback and recording. It also repairs any broken, missing or cross-linked codecs. (CoDec is COmpressor DECompressor). The renderer (player) could be so heavy and involved that it is using a lot of CPU resources, tasking your machine, causing the stuttering.
I hope this gives you insight into your issue. Good luck in your venture.