You will want to do the following:
Start > Control Panel > Add/Remove Programs > QuickTime > Uninstall Everything
After it is uninstalled do the following
My Computer > Local Disk (C:) > Windows > System32
Delete the following files
QuickTime.qts
Indeo4.qtx
QuickTimeMusicalInstruments.qtx
QuickTimeVR.qtx
(Don't worry if they don't all exist)
Download and install the latest version of
Quicktime (Quicktime v7)