Here's a summary, from this discussion thread and my experience, of the problem and a possible solution. Feel free to clarify or expand.
As I see it, there are two problems with the current version (7.04) of Quicktime for Windows:
1) movie clips have video but no sound either in Quicktime Player or in a Web browser via QT plug-in.
and
2) Quicktime doesn't uninstall completely, making it frustratingly difficult to downgrade to a previous version that does work. i.e., after unistall, installing QT 7.03 displays an alert that a newer version is already installed.
One might consider the fact that iTunes and Quicktime are so tightly coupled being a third problem. I don't know if an already-installed iTunes 6.0.2.23 (QT 7.04's version of iTunes) will work with QT 7.03, but I'm fairly certain if you install iTunes 6.0.2.23, it will upgrade Quicktime to the partially-functioning 7.04 version of Quicktime.
So, the current work-around is to use the Add or Remove Programs control panel from an administrative privileges account to uninstall Quicktime (and iTunes I would think) and attempt a downgrade to QT 7.03 and iTunes 6.0.0.18. As posted in this thread, the iTunes installer, "iTunesSetup
6.0WIN2KXP.exe", is available at
http://public.www.planetmirror.com/pub/apple/iTunes/
By the way, this might be overkill but before uninstalling iTunes/Quicktime, I also exited Quicktime from the system tray icon and stopped both the iPodService and iTunesHelper services. In XP Pro, it's Start:Control Panel:Administrative Tools:Services, find the item, open it and click "Stop".
If the downgrade installation fails with "newer version of Quicktime is already installed", you need to do additional file and directory cleanup before another attempt.
I found a post on "Manually Uninstalling Quicktime" post on this "Quicktime Error" discussion thread
http://forum.worldstart.com/printthread.php?t=65812.
Note, I only used the directory listing to check for uninstallation flotsam. You do have to have "show hidden files and folders" enabled under the Tools: Folder Options menu's View tab to see the items to delete. After your uninstall, look for Quicktime or iTunes folders, files, or shortcuts in these locations:
C:\Program Files
C:\Documents and Settings\All Users\Application Data
C:\Documents and Settings\All Users\Start Menu\Programs
C:\Documents and Settings\User Name\Application Data\Microsoft\Internet Explorer\Quick Launch
C:\WINDOWS\system32\quicktime
C:\Program Files\Internet Explorer\PLUGINS
I ignored the rest of that poster's message on manual registry cleanup, etc.
After my uninstall, manual file and directory deletion, and running Registry Mechanic to clean orphan registry values, I found I could install the working, earlier version of the iTunes/Quicktime bundle, "iTunesSetup
6.0WIN2KXP.exe", noted earlier.
Best of luck,
Paul
Dell 600SC Windows XP Pro