In the last couple of days, I've noticed that Quicktime has been assigning itself filetypes that I don't want it to open by default.

I've opened Quicktime twice now, and changed the preferences to not be associated with those filetypes. I've rebooted, and it's as if I never made those changes.

Are there any options before I uninstall it?

did you try setting the 'file types' tab in folder options? (which is in windows explorer->tools)

and make sure it's not the default media player in set program access and defaults

I cannot think of a reason to have it installed in the first place.

To watch movie trailers!

also to use itunes

There's probably a component in one of the startup locations that's resetting everything.

You have to have quicktime to run iTunes, and I have to have iTunes for now.

Anyhoo, yeah, I changed some of the filetypes in the folder options, but I didn't want to change them all manually.

I uninstalled QT and downloaded a new version and reinstalled. All seems to be working ok now.

Could've been the borked update that went out not too long ago. Quicktime always is let loose with ridiculous problems and bugs after every update. I had a similar problem, but running through the file associations list in windows fixed it.