quicktime player requires windows 2000 or later

get rid of 7.3 and go back to 7.2 there is a major bug in the 7.3 update just look at all the posts recently

http://www.apple.com/support/downloads/quicktime716forwindows.html
It's the last version that is supported on Windows 2000. Read the requirements.

Well I just started having this same issue in vista 64 ult.
So I removed 7.3 and installed 7.2 and get the same error still

QuickTime is not supported on a Windows 64 bit OS.
Change your "compatibility" settings to use 32 bit and see if it works.

+Hello, I can't use quicktime, it gives me the error " Quicktime player requires windows 2000 or later" and changes all my icons into super size. I have windows 2000 and I've disabled all in the compatibility tabs (as it requested) and this does not help.+

With that one, try heading back into the Compatibility tab.

Are any of the *display mode* boxes checked? If so, uncheck all of those too, and click okay. (They can also cause that message, and having one of those selected is consistent with your icons/desktop resizing.)

Any better luck with the launch after that?

Nope, nothing in there was checked.
So I uninstalled, rebooted, installed 7.15 and it worked.