Robert found your topic
I will try to help you out here.
You can record using both Webcam and Videocam. It helps if you record with better quality cam as picture quality (resolution) and lighting might become more natural.
You need two programs to make things work.
For Video editing you can use FREE software thats already in Windows. Its called Windows Movie Maker. You can find it under START/ALL PROGRAMS under your lower left of the screen. You will need that software to import already recorded video and audio file and sync it in it !
You can use another program, its called VEGAS. In a long run Vegas is much better software. Allows you to do many more things with video and audio editing. Thats why its expensive
However feel free to go with Windows Movie Maker for now, and in the meanwhile get TRIAL version of VEGAS and try to do things in it (it will make huge difference - much easier to work with!).
For Audio recording and editing you need some sort of DAW (DIGITAL AUDIO WORKSTATION).
There is many of these available, Reaper is used by a lot of GMC members since its FREE.
What you basically need to do in that software is open TWO AUDIO TRACKS, ADD BACKING TRACK ON ONE, RECORD YOUR GUITAR ON THE SECOND ONE. The final step is to EXPORT your recording.
In the whole process it is essential that you have DAW running and recording as your WEBCAM is recording !
That way you will have very quality source which you can later match in Windows Movie Maker !
I hope all this makes sense Robert, let me know if you have any questions !