Hard to answer without knowing what the "timeline problem" is  ...and what you are doing !

How do you know its a codec problem?

How about some more info also.

Assumeably you are intending to upgrade to CS6 before you give your computer to your friend.

That may or may not fix the issue with your "timeline". (It may install some system codecs you need or maybe not)

The  issue is more to do with the type of footage you have on that particular timeline in that particular CS5.5 project.

What is the footage codec that is missing?

Considering you are giving away the computer...that issue may not be a problem to the new user because he/she will be working with his /her own project and footage.

>never did answer your question

OK... here are the questions, again... with, again, the links to programs that will allow you to answer

What are you editing, and does your project match your video?

.

Read Bill Hunt on a file type as WRAPPER http://forums.adobe.com/thread/440037

What is a CODEC... a Primer http://forums.adobe.com/thread/546811

What CODEC is INSIDE that file? http://forums.adobe.com/thread/440037

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Report back with the codec details of your file, use the programs below... a screen shot works well to SHOW people what you are doing

http://forums.adobe.com/thread/592070?tstart=30

.

For PC http://mediainfo.sourceforge.net/en or http://www.headbands.com/gspot/

For Mac http://mediainspector.massanti.com/

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http://blogs.adobe.com/premiereprotraining/2011/02/red-yellow-and-gree n-render-bars.html

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If you have a red line over the timeline after importing a video and before adding any effects... your project is wrong for your video... read above about codecs

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Once you know exactly what it is you are editing, report back with that information... and your project setting, and if there is a red line above the video in the timeline, which indicates a mismatch between video and project

Also, the general questions you need to answer are in the Information FAQ http://forums.adobe.com/message/4200840

If you can't answer those questions, there is really no way anyone may help

The timeline problem was t6hat it wouldn't play back.

Are you saying...the timeline would play none of the media on it at all or ever?

See my comment above: let's try to create a new project from scratch - that may help us to understand and nail down your issue.

Well, so far I didn't see anything that would prevent PrPro from playing back your timeline. Could you upload this test PrPro project and one of the media files sample somewhere so that we can download them and test on our machines?

So as to share your files with us you can use any file hosting service available, e.g. Dropbox, FileFactory etc.

If you don't have an account on any of them, you have to create one (no needs to create any sort of paid account, free one is quite enough).

Once you created an account, a service lets you upload your files.

When a file has been uploaded, a service usually supplies you with a link to your uploaded file(s), which you can share with others.

So as to create a FileFactory account, you need to enter your e-mail, decide on a password, confirm it, enter CAPTCHA, tick 'I agree to the Terms' and click 'Create my account' button.

If you want to create a Dropbox account, when you fill in all the fields and click 'Sign up' button, an additional small Dropbox application starts downloading to your computer. You don't have to download and run it so as to be able to upload files to the service via Internet, but it simplifies the process a bit: this way you can just copy you files into the specially created 'Dropbox' folder on your computer, and the application synchronises your folder with your Internet Dropbox account.

Do not hesitate to ask some questions on how to use aforementioned services, if need be.

Go to your Dropbox account webpage, navigate to the files you want to share, hover a filename and click next to it - Dropbox highlights the line, and the 'Share link' option appears:

Click any of them - new window opens. Click 'Get link' button:

Link is copied to your clipboard. Paste it into your comment.

Got your project. Works fine with offline media.

Now share a media file sample.

By the way, which programmes have you got installed on your computer, aside from PrPro?

Well, I can playback both your AVI and MPG samples in PrPro with no issues. Let's try to move on:

1. What actually happens when you try to playback your timeline in PrPro?

2. Can you playback your timeline, if you switch Mercury Playback Engine to Software Only mode?

3. Can you 'playback' you timeline, if you make footages offline?

4. Can you playback a timeline created out of stills?

The latest update for PrPro CS5 is 5.0.3.

If you couldn't download 5.5.2 update, which is for CS5.5, it hardly had a chance to interfere.

If you managed to download it and then attempted to install... I don't know...

If you have the latest driver updates installed for your GeForce GTX 470 as well and still can't playback the timeline even with offline media (try Craig's suggestion about 'Bars and Tone' to see if it makes any difference, BTW), I'm almost run out of idea...

As just a ritual dance, try to

1. Clean up your Media Cache Database. Navigate to

     C:\Users\Ernie\AppData\Roaming\Adobe\Common\Media Cache and

     C:\Users\Ernie\AppData\Roaming\Adobe\Common\Media Cache Files and manually delete all files in both folders.

2. Deactivate and then reactivate PrPro

If nothing else helps, and some other worthies won't be able to give better advice, create backup copies of all files in Adobe directories you want to store, uninstall PrPro, probably, run Adobe CS Cleaner Tool and then reinstall PrPro...

There is something fundamamentally wrong with your system.

Suggest ...you give it to the kid and let him sort it (Kids are good at that stuff).

Shout your self a brand new system and CS6.

Check out this help section.