Download quicktime from http://www.apple.com/quicktime/download/ and try to play .3gp video files in it.

Quicktime plays .3gp files.. so installing it will resolve the issue.

When i first bought this computer, i downloaded and installed quicktime, and unluckily it didnt work, i got this Error message saying i could not open Quicktime . (But that isn't really important)

But even if Quicktime worked..i have alot of other players that could play .3gp files (VLC Media Player for example), i mean even WMP plays .3gp files, but the problem seems to be much more complicated :(

.3gp is not a file type generally recognised by Vista
VLC Media Player will play that and pretty muh any other type of file you can think of - music and video
In the setup of VLC in the advanced you can choose for it to load file type associations, and then all files that you have on your computer that VLC can play will be set to default open in VLC. However, you may want to stick with another player with some files so it may be easier for you to do it manually in the 'default programs' menu on the start menu

Download VLC here: http://www.videolan.org/vlc/download-windows.html
I find that the mirror form the University of Wisconsin always works fastest
Good luck!

Failing that, I missed the obvious - have you tried r-clicking and clicking open with?
or if nothing is recognised clicking on the unrecognised file, then when the window pops up syaing that windows cannot open the file, chosen from a list of programs on your pc?

@leeve

Thanks for your Reply, and i really appreciate your help!,
but about right clicking on the .3gp file , whenever i open a window that has a ".3gp" file in it, i will get the vista error message as explained above in the post!

so it isn't > Playing < the .3gp thats bothering me, it's simply accessing it/ using it.
But then again...Thanks for your help!

@Budohorseman. I am not overly keen on programs that do "everything". But this one looks impressive.

Ok, Thanks for your help guys...but i think i am being quite misunderstood here.
the problem isn't converting, i have Super ( and yes, it is Impressive ) but when i >Open a file with a (.3gp)
video file in it , i get the error message straight away!, thats the problem.
Thanks for your help anyway!

@ScottW
Thanks for replying!, i think you have understood me well :)
and i did try the "file association" and it was originally set to >RealPlayer< but i changed it to WMP thinking there was a difference..but unfortunatly there isn't.

And about the Thumbnail preview...i have a feeling im getting closer and closer to a soloution, i made the Thumbnail Preview as small as possible, and i didnt get the message....Until....i clicked on it to play it!
it loaded WMP but after a few seconds the WMP window turned white and the message came!

Ok, i am not going to give up, i think im nearly there!

xenomex: great news! I love it when a solution comes together.

I wonder if you would be interested in trying to diagnose the underlying problem. Although you can now open folders with .3gp files and play back in RealPlayer, there is still something on your system that chokes on .3gp files. If you want to continue this, I have some ideas about what might be happening.

But if you're sick of all this tweaking and would rather get on with updating your cell phone, I can let it go. If you stop now, but want to address it later, come on back and post again whenever you are ready.

xenomex: Good attitude! Let's get to the bottom of this.

Here's my thinking. A 3gp file is a kind of MPEG-4 video stream. If explorer would crash trying to render thumbnails, it was probably using a video codec, a DirectShow Filter, or a DMO to try and render the file. I suspect there may be a codec or filter problem. Since you are into video, according to your profile, you need to learn about this anyway if you don't already know it.

First, tell me what codecs you think you have, especially which one might try to render MPEG-4 files. Do you have any codec packs, such as K-Lite or CCCP? BTW, I personally do NOT recommend codec packs.

Next we will load up your video toolbox with some nifty utilities, though you might already have some. First, try the K-Lite CodecTweakTool which will check for broken codecs and DS filters and fix them. (The tweak tool is available without codec pack!) If that doesn't do it, next would be running a DirectShow filter graph to see what Windows is trying to use to render those 3gp files. That should do for starters. Get your tools at http://www.videohelp.com/tools

Post back with your results and any questions.