QuickTime locks up my XP - cannot play any .mov files?

[Jeff]

Every time I open Quicktime, or try to play a .mov file
my Windows XP (Home) Locks up. How do I play .mov files
on XP w/out locking the computer up? PLEASE help. Also
for any XP Pros out there - from a cold boot, it takes
about 5 minutes to get to the 'Welcome' Screen. It seems
to 'stick' on the Gateway Cube then a black screen for
about 3-4 minutes, etc...

PLEASE HELP - Thanks!