There are some solutions to convert jpg file to vector file, for instance, using corel draw, adobe illustrator or adobe photoshop…
For me, I’m much familiar with photoshop, so PS would be my first choice. ^^
Here is a very simple but useful tut :
http://www.bittbox.com/illustrator/take-vector-paths-from-photoshop-into-illustrator
what if you have an jpg image needed to convert to vector paths?
1. Open the image by photoshop
2. Make selection

3. Remove the other objects you don’t need in the picture.

4. right-click in the selection area, than choose "make work path"

5. Export to illustrator : File > export > paths to illustrator, than you will get another new illustrator file.

6. Open the illustrator file you just got on last step, you will see a blank page, don’t worry, it does has the paths, just select all things on the page,
you will find them out. Because those paths have no color. The final step is to paint the paths by the color tools in illustrator.
There you go… we have a vector image as same as jpg image.
