You need QuickTime installed to watch videos in SL: http://www.apple.com/quicktime/download/
Sometimes a video won't play. Sometimes this can be fixed by clearing the various caches:
First thing to try is clearing the QuickTime cache. In Win XP:
Settings / Control Panel / QuickTime / Advanced tab / Download Cache, "Empty Cache" button
Second thing to try is clearing the SL cache:
Edit / Pref / Network / Disk Cache Size (500 MB) / Clear Cache - requires restart of SL
Third thing to try is clearing your web browser's cache
(this works sometimes also if a video on YouTube says it's unavailable). In IE:
Tools / Internet Options / General tab / Browsing history / Delete / [check] Temporary Internet Files / Delete
If that doesn't work this is what you have to do on windows
This is how I fixed QuickTime on my system (XP). The videos were starting, and then getting stuck.
I don't bother installing iTunes. It's a huge download, and there's always an update, which takes more time. Whenever I would use iTunes, that's when I'd get the current version.
De-install QuickTime in Add/Remove Programs
Some don't like registry cleaners. I had felt this way, since you can mess up your whole computer if you're not careful, but I've had no problems. If there's a problem with a program, I think the best way to fix it is to just de-install, clean, and then re-install the software.
Do a Restart
This might not be necessary, but it's another option to try. In XP, from a DOS prompt, run the System File Checker to verify that all protected Windows files are intact and in their original versions. It takes one minute. It won't work in Safe Mode, it says the RPC server is unavailable.
C:\>sfc /purgecache
C:\>sfc /scannow
Do a Restart
Re-install QuickTime
Within QuickTime:
Control Panel \ QuickTime \ under these tabs . . .
Browser \ [check] Play movies automatically
Streaming \ Automatic, [check] Enable Instant-On, slider 1/4 from the left
File Types \ [click] Use Defaults
Advanced \ Download Cache Size 547 MB, [click] Empty Cache
In SL: Edit / Pref / Network / Maximum Bandwidth / 1300 kbps . . . make sure this is set correctly, verify your speed here . . .
http://ww.speedtest.net/
In SL: Edit / Pref / Network / Disk Cache Size 500 MB . . . I had this set at 250 MB, and the vids got stuck. Changing it to 500 seemed to fix it at one point.
Other ideas:
I had a 768 kbps connection, tried everything, and determined that it was too slow for video. 1.5 MB works.
I had multiple copies of Sun Java on my system. Un-installing those made my computer faster.
I use AVG Free anti-virus. Resetting all of the "Scans" to default made my computer faster.
Two other free utility programs I can recommend:
Patio quoting Slack Gigamon
