Vond nog een leuke tutorial voor het omzetten van de .3gp filmpjes naar een avi formaat, en heb het hier geloof ik nog nergens echt duidelijk zien staan

( wel van avi naar 3gp maar niet andersom )
How to convert .3GP movies, taken with mobile phone, into .AVI ?
Convert 3gp to avi with QuickTime Alternative and Zwei-Stein Converter
Download freeware
Zwei-Stein Converter.
Next, download and install free 3gp codecs intended for converting files:
Quicktime Alternative.
1) Launch Zwei-Stein (Click Start -> Programs -> Thugs at Bay...)
2) Press File -> Import -> Import Video Clip
3) Select type of files - "All files (*.*)"
4) Open your .3gp video clip.
5) Press File -> Export -> Video for Windows (AVI)
6) Enter filename.
7) Choose video codec. DivX, XviD or WMV9 are recommended.

Click OK! That's all.
NOTE: You can change several parameters before conversion
- Video Dimensions (menu Destination -> Video Format)
- Video Frequency (menu Destination -> Frames Per Second)
- Effects (menu Source -> Add Video Effect)
Andersom ( van avi naar 3gp ) Freeware mode
The most easy way: download Nokia Multimedia Player with 3GP support.
Download it from here:
http://www.nokia.com/nokia/0,8764,42291,00.html (8MB)
This is normal video player for PC platform (Windows OS), but it has several additional functions (conversion to 3gp format).
1) Download and install player.
2) Launch Nokia Multimedia Player. Open your video file (avi or mpg).
3) Press File -> Save as...
4) Enter filename of your 3gp file, and choose resolution and size limit:
MMS 64KB, 128*96
MMS 95KB, 128*96
MMS 95KB, 176*144
Custom 200KB, 128*96
Custom 200KB, 176*144
Custom 300KB, 128*96
Custom 300KB, 176*144
No size limit, 128*96
No size limit, 176*144
5) Click Save. File converted. That's all!