I have MPEG movies taken on a domestic Sony Cybershot pocket camera
that I have taken in portrait format.

I need to rotate these by 90 degrees so they can be viewed. 

Where can I find some shareware etc to do this? And how? 

Thanks!

Hello jjfap-ga

Thank-you for your question.

The easiest and cheapest way to edit your video so that it is rotated
by 90 degrees is to download and use VirtualDub.  This free piece of
software can be downloaded from their site here:

http://virtualdub.sourceforge.net/

The homepage for the software is available here and includes links to
several useful documentation pages and the program's forums:

http://www.virtualdub.org/index

Without knowing how much experience you have in editing videos on a
computer it is difficult to guide you through this so I will initially
be brief in my instructions.  Should you require any further help
please ask for clarification and I will do my best to respond swiftly.

1) Download and install VirtualDub from the website indicated above.
2) Run the program and open your MPEG into the program.
3) Go to Video under the menu and click Full Processing Mode.
4) Press Ctrl-F (or go to Video->Filters) to open the Filters Dialogue box.
5) Click Add and choose Rotate from the filters shown.  You will have
the option then to choose how you wish to rotate the video.
6) Click OK to get back to the main VirtualDub program window.  You
may now do any further editing you require to the video using the
program.
7) To rotate the video you should now save the video as a new file and
the process will begin.  Please note that this may take some time
depending on the speed of your PC and what further options you have
chosen.

There are several excellent beginner's guides to VirtualDub on the
internet a few of which I have linked to below.  Once again, should
you require any further assistance please do not hesitate to ask for
clarification.

VirtualDub Tutorials:
http://www.windowsmoviemakers.net/PapaJohn/16/VirtualDub_NanDub_Tutorial.aspx
://www.google.com/custom?q=virtualdub&submit.x=0&submit.y=0&cof=LW%3A640%3BL%3Ahttp%3A%2F%2Fwww.digital-digest.com%2Fimages%2Ftitle.jpg%3BLH%3A140%3BAH%3Aleft%3BGL%3A0%3BS%3Ahttp%3A%2F%2Fwww.digital-digest.com%3BAWFID%3A4fa764bb47b45cb7%3B&domains=digital-digest.com%3Bdivx-digest.com&sitesearch=divx-digest.com
http://www.tech-recipes.com/pocket_pc_tips529.html
http://www.videohelp.com/guides.php?tools=2&madeby=&formatconversionselect=&howtoselect=5%3B&orderby=Date&listall=1&hits=25&archive=%25&listallusers=&search=Search+or+List+Guides
http://www.doom9.org/index.html?/virtualdub_procedures.htm
http://shanebrinkmandavis.com/homepage/Archos/Main/VirtualDubTutorial/

Superb!  Thanks!