Several questions here...
RE:
I haven't installed the Canon software, I am using ACD to manage
all my image files so far (by the way, is Canon's a better software
in post-processing compared to ACD ?)
I am NOT a post-processing guru by any means! I've diddled with a few scanned images from time to time, but nothing serious. With that open admission of my ignorance

, here's what I know and don't.
I am not familiar with "ACD"...not even sure what it stands for.

I also have not loaded and never used any of the Canon software - either to manage the images (move them around or catalog them) or to post-process them. So I can't tell you if one is better than another.
RE:
Instead of using the USB
cable, I read my images from a card reader. The movies show up as a
.AVI file too. But I just don't seem to be able to see my movies
whenever I put my CF card back to my V3.
OK, what I understand you are doing is take the card from the V3, put it into the USB reader, use some sort of software (ACD?) to either open or somehow do somethign with the files on the CF card. When you take the card back out of the USB reader and put it back into the V3 you cannot play the movies on the V3 anymore. Right? I assume you were able to play those same movies on the V3
before you took the CF card out of the V3, etc., etc. Right?
If the answers to all my "Right?" questions is "Yes", then what is happening is that the software that is touching the images on the CF card is modifying them on the CF card in such a way as to make them unreadable by the V3. There is a note in the FAQs on the Canon
http://www.powershot.com website warning that certain Microsoft-supplied programs (I think it is the Windows Picture and Fax Viewer that is part of explorer.exe on Windows XP) will do this if you rotate an image on a CF card with that software and try to read that same image again on the V3.
I was hoping to put all the movie clips I made under a folder
called "My movie" (it's on my desktop, otherss include "My
pictures" and "My music" etc but when I tried to open the file, it
says the file doesn't expect ? If I could save my images in the HD,
why not the movies ?
What software are you using to do this? ACD? If ACD, I'm sorry, I can't help you since I don't know that software.
What I have done (not with a USB CF card reader since I don't have one) is this. I am running Windows XP Service Pack 1, but this should work for Windows XP w/o Service Pack 1, too. Earlier versions of windows may not work the same since WXP has a lot more awareness of multimedia devices than earlier versions.
I connect the USB cable to the camera and the computer. The camera shows up as a disk drive on the Windows explorer. I click on it and it gives me a list of files. I drag and drop those to a folder on my hard drive (using Windows explorer - no other software running. I have also used the Scanner and Camera Wizard to copy files from the camera to the hard drive. Both of these methods simply transfer the files unaltered to my hard drive. Using a CF card reader should be even easier - just drag and drop to a folder. This method has moved jpg and avi files just fine.
After the transfer, I open the copy of the files on the hard drive (not the CF card) with whatever software I want to use. This way, the copeis of the files on the CF drive remain in the exact format as created by the camera.
I then write-protect (right click, properties, Read only) all those files on the hard drive. If I want to modify them, I copy them to
another folder and modify that copy. That way, I also have a master as-it-came-from-the-camera copy of all my images on my hard drive. If I screw up any mods, I can always go and fetch another copy of the image from the first folder.
What other software am I using? The only mods I have made have been simple ones - rotating, cropping, resizing, etc. I have use Microsoft Photo Editor (comes with MS Office, but not standalone) for years to do these simple operations. I like it because I know how to use it - and because I already had Office it was "free"!. I use Thumbs Plus as my image cataloger. It understands EXIF and will not delete EXIF information. Plus it allows me to create a full database of thumbnails and add as much associated information (in addition to the EXIF), like keywords, as I want). It also does a variety of usual and normal post-processing tasks. You can download a demo copy from cerious.com and try it out. It is only $70-$80 for a full license. When I start to get really serious I will probably opt for PhotoShop, but I might start with the much-less-expensive PhotoShop Elements.
But note - I do not use MS Photo Editor, Thumbs Plus or anything else to open the files on the CF card - just use the copy facility built into Windows to get the files off the CF card and onto the hard drive - then mess with 'em.
Hope this helps!
Greg
--
Canon S230, 128Mb Ridata
Oly Stylus 105
Nikon FE (2), buncha Nikor glass, motor winder, Sunpak flash