When using Quicktime 3 for Windows with either Windows 95 or Windows NT, you may experience QuickTime videos that play slowly.
DISCUSSION
Under Windows, DirectDraw is recommended for optimal performance. Since QuickTime can take advantage of DirectDraw and DirectSound, it is important to have the latest drivers for your video and sound cards. You also need the current version of Direct X.
One place to check for latest drivers and Direct X is at Download.com: